Ask HN: What are your recommended reads that are available for free?

I recently stumbled across a link in another thread to "Economics in One Lesson" and thought it was incredibly interesting. https://mises.org/sites/default/files/Economics%20in%20One%20Lesson_2.pdf

What are some other interesting reads—whether PDF, website, doc, etc—that are freely available?

One of my favorites that I find thought-provoking is the "Procedural Content Generation in Games" book (http://pcgbook.com/).

I love "Operating Systems: Three Easy Pieces":

http://pages.cs.wisc.edu/~remzi/OSTEP/

Really useful book and really accessible (both because it's available for free and also because it's written with a lot of skill and friendliness towards the reader).

I recommend it in particular to those who for whatever reason never took an operating systems class (e.g., you were self-taught or didn't major in CS). This book will really demystify a lot of stuff for you without overwhelming you at the same time.

Sicp is available for free

https://sicpebook.wordpress.com/ebook/

Steal This Book: https://leanpub.com/stealthisbook (Apparently no longer available from LeanPub... heres's a dropbox link: https://www.dropbox.com/s/qm6vkabvd8jc3le/stealthisbook.pdf?... )

Don't Just Roll the Dice: http://download.red-gate.com/ebooks/DJRTD_eBook.pdf

If your preferred book isn't available for free, it usually means you haven't tried at Library Genesis.