Ask HN: What Programming Book would you buy right now (if it existed)

Whacked from reddit (http://www.reddit.com/r/programming/comments/8aixn/programming_books_that_you_would_buy_right_now_if/?sort=new), but I would love to hear HN users's opinions.

I would buy "Inside The Python VM", (replace Python with Erlang or Lua or V8) and "A Hacker's Guide to Hadoop Internals"