The bookshelf

You're instantly drawn to the bookcase, checking the books on its shelf. You had been told this cavern was a place of depravity and darkness - books in an old room were prime places to find information as to why.

The bookshelf is a simple thing- wooden, only one shelf, and with only three books. You can make out parts of two of the three titles- the leftmost, small and green, has something to do with "Survival" and "Plants." In the middle is a moderately sized red book, reads "Dangerous Creatures and" before cutting off. The final volume is large, brown, and bound in leather, with no discernible words on the side. An ornate pattern of metal diamonds adorns the ends of the spine. Strangely, the bookshelf seems to be more knotted and rotten on one half than the other, as the right side almost looks ready to collapse at a single touch, and the grass directly underneath is withered and brown.

You decide to carefully reach out towards the large, leather-bound book. The instant you remove the third book from the shelf, it collapses, falling into a pile of dust on the ground.

The thick leather volume has no discernible markings on the front- no title, author, or any other distinguishing remarks. When you open the book, it seems like it's not even in English- each page is in a set with the one across from it, one page with two pictures and the other with strange lettering, words that you don't understand. The first few pages are rather mundane- the first depicts a woman twice, the only difference being her hair color. On the second is a pair of men, with one appearing to be slightly taller.

After a few more pages, you turn an additional page and gasp. A woman is drawn, twice, fully naked, with the picture on the left featuring a larger pair of breasts. The next page is similar, except with a naked man, his penis larger on the left. On the next two pages are the same, except reversed, with the "larger" person on the right. Another page displays a woman lactating, and another shows a man ejaculating. Later in the book come even stranger pages- pictures on the left start to feature animal parts, from hooves to frog flippers, cat tails, and even one page with a very detailed drawing of a horsecock. There's even a woman with what looks like squid tentacles extending from her back. On the final page, there's only one image- a large pentagram, with a humanoid form extending out of it.

Each of these pictures seem to correspond to a single sentence, and it's likely that you could attempt to phrase them, though the words look absolutely nothing like English.