On a living planet, nothing lasts forever. Especially if you're limiting the number of iterations of each book to one. One book per topic (e.g. Shakespeare) per place (is that household / city / county / nation / planet?) is asking for disaster, and even more disaster as you move from left to right along that scheme!

That said, there are several time tested possibilities:

Clay Tablets

The "Assyrian National Library", sponsored by Emperor Ashurbanipal at Nineveh, is the oldest surviving royal library known, dating to 700BC or thereabouts. Clay is easy to write in and once fired, the tablets are sturdy. They're a pain in the backside to deal with for texts of any great length or complexity. Can last thousands of years if well cared for, or if abandoned and forgotten for millennia.

Stone

Egyptians carved literature into stone. Like clay it's durable, but is not indestructible. Like clay, it's a pain to maintain lengthy texts. Can last myriades to millions of years if protected from erosion

Papyrus, Paper & Vellum

Well known to ancients & moderns alike. Easy to make & convenient to write on. Durable and long lasting. If you're people are repairing books every decade, then I'd say they are either overly abusive towards books or else don't know to bind books. A book printed on good rag paper and well bound can last several centuries without needing more than minor repairs. When well maintained, books of this sort can last many centuries: expect somewhere between 13 and 20 centuries. All these materials will eventually decay, even in the best of conservatories.

Metal

This is probably the most durable option. Books have been written on gold pages, the oldest of which are in the region of 2500+ years old. Copper / bronze, stainless steel, gold, platinum: any of these should last indefinitely under stable atmospheric conditions.

To Digitise or Not to Digitise?

Even the best digital media will find it difficult to compete with well curated books. Digital media are also heavily reliant on external factors such as electricity, computers, operating systems, stable cultures & societies just in order to be accessed & processed. Whether it's magnetic or battery supported or flash memory, digital media are not a good idea for truly long term archival of a culture's most important data.

Conclusion:

I'd recommend that the culture's most precious data --- scripture, literature, mythology, folklore, poetry and the like --- be preserved on metal plates. And also on high quality paper books bound in solid & protective hard covers.

All rapidly changing data --- scientific & technical developments, rapid advances in medicine, changes in law --- should be committed to okay quality paper.

Ephemeral data --- accounts, receipts, bills, notes and so forth --- these don't need to be archived at all and can be kept on cheap paper.

Plain old ink on vellum scrolls.

You want books that can be added to and that don't need replacing very often. They don't have to "live forever" as your title implies, because you say "my species is focussed upon scientific advancement and probably won't want to be tasked with repairing broken books after each decade." So repairing every couple hundred years and replacing every (half) millennium should work.

This is a closeup of the actual Torah scroll at my synagogue. It's written with a natural ink designed for preservation on deerskin vellum (deerskin is very unusual but allowed). The scroll was written by hand in the 1700's and used regularly by a synagogue in Europe until stolen by the Nazis (who murdered all the residents of the village) and put in a warehouse for decades.

It was donated to a nearby synagogue likely in the 1960's, then transferred to us. It lives in a cabinet that has no special environmental controls. The scroll consists of sections of vellum stitched together then rolled up on wooden rollers. It is tied shut with a ribbon then covered with a cloth and stored upright.

This scroll is handled regularly. Many synagogues pull out their scrolls and read them several times a week (they often have several scrolls they rotate), others less often. Any given scroll might be exposed to air and movement a couple dozen times a year. We use implements to touch the writing so our hands do not leave oil and dirt, and the scrolls are handled with care, but basically there isn't a lot of special treatment. We never wear gloves or anything like that.

There is some maintenance involved, but nothing major. The scrolls should be cleaned every few years. The covers get replaced now and then. I'm not sure if our wooden rollers are original (probably not) but every 100 years wouldn't be unreasonable for replacing them (your society could use a more durable material, like metal).

So this scroll which is around 250 years old is definitely fading and has a couple of stains and the vellum is eroding a bit on the edges. But it's still in use and is completely readable.

For a non-sacred scroll, go ahead and use a printer to apply the ink (there's nothing special about doing it by hand in terms of preservation). If you want to add to the book, just sew on a new panel (on the ends or even in the middle...panels do get resewn if needed for maintenance so this is very doable).

Will it last a millennium? Perhaps not. But half a millennium is very likely, baring disaster or poor caretaking. Pieces of scrolls almost 2000 years old are still readable, but going that long does deteriorate them, so I wouldn't go longer than 500 years (less is safer but perhaps not necessary).

So what do you need:

• Basic reasonable care in avoiding finger touching, using a cover, keeping it dry, etc.


• A light cleaning and check over every 5 years or so.


• Replace the cover once or thrice every 100 years.


• Consider replacing wooden rollers every 100-200 years, or use another material.


• Sew in new panels as needed.


• Reprint/write every 500 years or so.

Fused Quartz Etched by Femtosecond Laser

Some articles on this technique here, here and here, and a wikipedia article with more references here. According to that first article,

The current data-writing system is not much different from that found in CD or DVD drives. Ultrashort laser pulses with a wavelength of 1030 nm are focused inside a spinning glass disc and the position, power and polarization of each pulse are simultaneously modulated depending on the encoded information – leaving a trace of pits with different optical characteristics. Reading the data is more complicated because it requires a microscope-based birefringence measurement system, but we are now working on how to solve this problem.

The original paper says that they estimate how long the data will last by looking observed decay rate of the nanovoids (the 'pits' made by the laser as mentioned above) at "several annealing temperatures in the range from 1173 to 1373 K", and then using the Arrhenius equation to extrapolate the decay rate at other temperatures. In fig. 4 they present the following chart showing the "thermally activated decay time" $tau$ (which they mention is equal to $1 / k$, where $k$ is the decay rate in the Arrhenius equation) as a function of the temperature $T$:

So, though one would have to preserve the fused quartz records in a place where they will be extremely well-protected from shattering (as fused quartz is a type of glass), the time that would pass before the information would degrade due to ordinary thermal decay is extremely long--longer than the current age of the universe (13.8 billion years) at a temperature of 462 K (189 C) or less, and $3 * 10^20$ years at a room temperature of 303 K (30 C).

More generally, ever-increasing number of backups are needed for arbitrarily long timespans

Ultimately if you are concerned about your civilization preserving the information indefinitely on cosmological timescales (as suggested by your comment about assuming they can avoid heat death and proton decay), you will want the civilization to periodically make new backups and store them in different locations throughout the universe, so that the probability that all records of some information are destroyed is continually decreasing over time. If the probability of all records of some information getting destroyed isn't decreasing this way, if you wait long enough it becomes a virtual certainty you'll lose that information. Say in a given million-year timespan the probability is $q$ that the civilization loses some item of information due to all records of it getting destroyed, so the probability the information is preserved in that timespan is $(1 - q)$. Then naturally if the probability is same in the next million years the total probability the information will be preserved for 2 million years will be $(1 - q)*(1 - q) = (1 - q)^2$, if the probability remains constant for 3 million years the probability the information is preserved in that time is $(1 - q)^3$, and so forth. No matter how close $(1 - q)$ is to 1, there's going to be some sufficiently large exponent $N$ such that $(1 - q)^N$ becomes arbitrarily small.

On the other hand, suppose the probability the information is preserved in the first million years is still $(1 - q)$ but the probability it's preserved in the next million year span is $(1 - q^2)$ and the probability it's preserved in the next million year span after that is $(1 - q^3)$ and so forth. So here the probability the information is preserved for 3 million years is $(1 - q^1)*(1 - q^2)*(1 - q^3) = prod_k=1^3 (1 - q^k)$, using Pi notation for products akin to Sigma notation for sums. Then if that pattern continues indefinitely the probability the information is preserved approaches a nonzero limit $prod_k=1^infty (1 - q^k)$, which according to this mathematica page is given by the Euler function $phi (q)$, and the page also shows a graph of its value for different values of $q$. So this limit can be thought of as the probability the information is preserved forever, assuming a universe where a civilization surviving forever is physically possible (I talked about that question in this answer), and where they are able to create an ever-decreasing probability of losing all copies of some record by the method of ever-increasing numbers of backups.

Grey Goo

Sure it looks like a book. It feels like paper. But it is actually a colony of self-replicating, self-repairing, self-updating nanites. They are not sentient, and are designed in such a way that they can't run wild and consume the whole planet or awaken.

Any damage is repaired by repairing the individual drones, or disassembling and building new ones.

When I say self-updating, I simply mean the knowledge they contain and display. It maybe automatic, or may be through a specific process. It maybe that the nanites are able to translate words written on them in ink/pencil into their database, probably comparing and validating it.

To recycle one of my other answers, have a read up on the Rosetta Disk. This is an information storage system intended to survive at least 10000 years and still be consumably without seious technology.

Basically, you use techniques derived from semiconductor fabrication to inscribe information onto a physically robust substrate that can then be read back via visible light or electron microscopy. You can aid this process with mechanical and electronic devices. Information density is limited, but its toughness and longevity is much higher than any electronic storage mechanism. Whenever you do an update, just mark your old copies as obsolete (and make sure your new copy is correctly versioned and dated so you don't read old stuff by accident!).

Rock and Bone

We have good bone fossils from hundreds of millions of years ago, and other fossils are even older (up to almost half a billion years for some bacteria).

Your books are fossils encased in cubes made of bedrock. They are read through ultraprecise echography.

Potshards are highly durable. A potshard is a fragment of pottery found in an archaeological excavation. In many cases an entire cup, bowl, amphora, etc. is found in pieces, crushed by the weight of material on top of it, and is glued back together and displayed in a museum.

So if a way to manufacture potshards (instead of entire pots) of the right size and shape to resist further breakage is developed, they can than be printed with data. Presumably a printing press can be developed with plates curved in the same way as the potshards and the pieces of type can be positioned in the plate similarly to regular printer procedures.

Possibly the press will print on the surface of the potshard with ink of some kind and it will then be glazed to protect the ink.

Or possibly the potshard will be still soft and the type will press into the soft clay and make depressions for the letters and numbers. Then the potshard will be fired to harden it and make the letter & number shaped depressions permanent. Possibly material of a highly contrasting color will be poured into the depressions to make them more visible.

Since all the potshards will manufactured with the same sizes and the same degree of curvature, they should be simple to store. And if there is a disaster they should still be legible millennia later if found by archaeologists.

Of course if the society is advanced enough to have digital storage methods, it will have more advanced methods of creating potshard like "pages" of writing. And may other possible materials, not just pottery, for the archival writing.