What's the last book you read where, if asked whether you thought reading it had been a good way to spend your time, you would not just say "Sure, I think so," but "Hell yeah!"?
I went through my last couple years of reading and seem to have a rate of about 1 in 10 hell yeahs. Most recent hell yeah is Tehanu, in the Earthsea cycle by Ursula K. Le Guin, and in nonfiction, Freedom Ship by Marcus Rediker.
@scott tehanu is great. Recently hell yeah reading... Tusks of extinction (short story) Children of time (novel), there is no antimemetics division (novel)
@scott My answer probably is of little help to people who aren't math nerds, but it is the HoTT Book (a mathematics text, and there are actually caveats about which sections I read, which ones I skipped, and whether it was the read itself or all the mathematics I learned spurred by the book as much as the book itself).