Contrary to my perception of public belief, I think the best way to learn a new subject (or gain more depth in a familiar one) is to find a good book on it and start looking for new ideas in it.

#Public Library

This is a collection of books I like and/or am reading (or intend to read heh.)
I used to collect books from libgen but 1) have switched to backup methods that make that difficult and 2) feel guilty for being such a pirate.  

Therefore, from now on I'm only collecting books that can be redistributed (or are available on archive.org)

I'm starting off with some of the Mir books since it's that publisher who has convinced me that maybe there's enough out there that I shouldn't be pirating.

#Note about undergraduate texts

Unless it's in a subject I'm not familiar with I probably won't keep much undergraduate stuff here. There's plenty on libgen if you want it. I don't have a favorite LA book since when I took the class the professor didn't give us one and only gave us lecture notes. I think the MIT one is publicly available, and I read most of Anton's while taking calculus. Both of those are bent more toward application though and that's why I hesitate to call them favorites

#Note about art and music books

There are very few publicly available E-books (pirated or not) on art and music theory as far as I'm aware (I'd love for you to disagree with me --swiley@swiley.net) The book I've been going through on music theory is titled "harmony." I think you can get it on amazon, I found it in the back of my favorite used book store in Lynchburg and it's signed by a "Dean Howard." ("1962") If you google very hard you can find an *extremely* low quality scan of the book, it's dense enough I would recommend not bothering with that though.  

Finding books on music theory is hard enough, finding good ones is an almost impossible task, finding free E-books on it is likely actually impossible.