I just looked through some random books/mangas I had laying around. I saw some (what I believe to be) unique arts, so some extensive species collectors might collect books as well. They do take up a lot of space and the specific arts one would be interested will be hard to display. There are pros and cons so I wonder how these collectors view books?
Some examples:
I don’t really pick anything up unless it is prominently on the cover/outside with the ability to be displayed.
Unless it was on the cover I wouldn’t really consider it. Which even that is super far removed and niche.
For me it honestly depends on a few factors:
I only have a few at the moment as I prefer to keep magazines and pamphlets (easier to store) but the ones I do have are a grand exception.
Shogakukan’s “Pokemon no Shima” by the Cabin Company has so much charm and I absolutely love the chaotic art - gives me Komiya vibes - it ticks off all of the boxes for me:
Most recently I was able to find this book that a fellow species collector - Retrosteelix - informed me about called, “Let’s Play with Pokemon English”. Most of the book doesn’t do much for me but it does have a unique depiction of Red Gyarados which hasn’t manifested in much publications outside of black and white comics:
I also bought the entire original PiPiPi series by Yumi Tsukinino. I went on a Tsukinino craze for the better part of 2022 after discovering her artwork in Ciao Magazine and desperately hoped to find artwork of hers that had a Gyarados since I did find a card of hers which had a Magikarp. Although there were no cards or stickers, it turns out two volumes of her original series had a Gyarados - one was a Ditto in disguise. This one also ticks off all the boxes for me:
But my absolute favorite appearances of Gyarados are in the 4-Frame Gag Theatre Comics which are books that feature 4-framed one off comics. It ticks off all of the markers for me (several appearances, multiple art styles that I enjoy, incredibly unique appearances, Japanese exclusive) Gyarados appears in a bunch of them and have varied and wonderful appearances (see more images in the slideshow):
Because books are a hassle to store, I tend to avoid them. But if they have unique art, I like the style, there are unique depictions, and it’s a Japanese exclusive? Then I’m more likely to acquire it.
I like the unique art of some of the early books. Gives a lot more perspective to the world of pokemon. I dont think id get them just because of the species or artist collections but moreso because I just like them.
I consider books to be separate from the TGC collecting, at least when it comes to art collecting. If you’re getting a corocoro magazine because it has a sealed promo in it, I get that, but in my head art-wise they are 2 separate categories of collecting.
Love to see all the answers, I bought a lot of books in one buy sometime ago, and some of them are so unique and while I would not have bought them seperately I am happy to own them now. They are nice to scroll through with art styles you would rarely see elsewhere.
That gyarados in the pokemon no shima book is amazing, I am happy you shared that!
I personally consider them when Seviper is visible on the outside, whether it’s the front or back. In some cases this is extremely small, like this magazine with a tiny Data Carrier Seviper figure at the back:
Although tbf, I already owned this magazine long before I started collecting non-TCG Seviper stuff. And it also got some unique Seviper manga on the inside. 
Thus far I’ve made one exception where Seviper isn’t featured on the outside, since I really liked the Seviper artwork on one of the pages, which is this one:
Greetz,
Quuador
I need Swinubs Nose so badly
I’ve bought few examples from some of my favourite artists for unique artwork they provide but the amount of work and money it would require to get info of the artwork inside all the books and manga + then obtain them doesn’t give enough reward as they indeed are difficult to display, store or even understand the context for one not speaking japanese. Would love to one day get deeper there but atm if it can’t be placed in binder or in display cabinet it doesn’t feel as special to me as other items
I think if I happened upon the item or really liked the comic/book/manga or unique art, I might stick it in the species collection, but I probably wouldn’t put it very high on a priority list of items to get.
If my species were in a Pokemon Tales book though (like below) I would totally need it. (Like @implode and Swinub’s Nose)
Hmmmmmm… 
