I'm not sure whether David Mackay's Information Theory, Inference, and Learning Algorithms (freely available at http://www.inference.org.uk/mackay/itila/book.html) counts as a textbook, but it's one of my favorite books, on any topic, in any genre.
Had. Unfortunately Professor MacKay passed away from cancer in 2016. We lost a great soul.
I concur that his textbook and sense of humor were fantastic. It was very enjoyable for me to learn the material from his lectures. They are a great supplement to the textbook (or maybe vice versa?) and you can find them here: https://youtu.be/BCiZc0n6COY
