1. The room that has slowly grown back into trees and skin. The trees have not yet shed their ink so you can enter into their crumbly trunks and read most of their secrets still, although you will need a torch and some patience and to know the right song to open the tree back up should it slam shut on you. The skin is mostly confused; it has formed back into limp, meatless cows which flap in the breeze from the air conditioning unit.
2. The toilet. Legend has it that there is only one toilet in the library; it is merely very busy in space and time. This is why there is always the same dog-eared book of cartoons on the shelf. Enterprising explorers have been known to stash energy bars in the cistern for emergency retrieval once lost in the booky depths.
3. The room you get into by opening that very small book on the bottom shelf and reaching your hand into the hole on page twelve to flip up the latch in the room beyond, after which you can open up the large book on the stand and enter through any of the doors on pages six, twenty-eight or one hundred and sixteen at your leisure. I do not know what is in that room, because my hand is too big for the hole in the small book. But yours may be smaller.
4. The large large print romances section. No, larger than that. Larger than that, too. It is not so much an area for the partially-sighted as a lobby for massive letters to hang around in, posing and slouching and occasionally making words, but mostly making out with each other. At least one of them is probably a colossal squid and not a letter at all, but every time it faces suspicion it covers itself in ink and that will do, for this place at least.
5. A room of propaganda. It has a number of entrances; based on certain aspects of your appearance and personality, the librarian will recommend an entrance for you if you want to first be exposed to propaganda only against them and not you. But the room is so designed that you can always look up and see them as they sit and read texts about you. Given the vast asymmetry in the amounts of propaganda available, its geometry is a marvel to behold.
6. The room where they keep the books that you write in your dreams (not the ones you would like to write; the ones that you write in your dreams). You may not remember the dreams, but there they are. It is a round room with one great spiral shelf, starting with the tiny books you wrote in infancy and progressing onwards and upwards through taller and thicker tomes. There is a ladder, should you need one. You are not sure if they stop at now or not.
7. A room of infinities and of their puzzles and paradoxes. Perhaps surprisingly, this is right at the entrance of the library. Of course, the way back out from there is infinitely long. There is a sign stating this at the entrance of the room and for some reason, perhaps some slavish devotion to conventional notions of space and time that we in the library have quite transcended, nobody takes it seriously enough. Anyhow, there is a mirror in there where you can find your other sibling, the one who always when you never and vice versa and so on.