Princeton Bitcoin Textbook

In case you hadn't heard Bitcoin hit at an all-time high of over $2,400 USD / BTC today.  There's plenty of good cursory information about Bitcoin but if you're looking for a decent in depth discussion of Bitcoin, related protocols, and other associated topics check out this book published by Princeton University Press.  The book is particularly suited to readers who already have an understanding of cryptography, computer science, networking etc.  If you're interested in going even deeper there's also a Coursera course to accompany it developed by one of the authors of the book.