Books by Dr. Donald Knuth are as close to error-free as I've ever found --- and best of all, if one finds an error, one can send it in and get a reward.
See:
http://www-cs-faculty.stanford.edu/%7Euno/books.html
I received a (physical) check for $2.88 for finding 1 error in his book Digital Typography (pointed out that Monotype metal casting machines was a proper noun, whereas the monotype process was a different thing) --- $2.56 and an additional $0.32 for suggesting a point of improvement (mention that a later version of TeX had made it possible to spell a word differently when it was hyphenated).
http://www.quora.com/Donald-Knuth/If...did-you-get-it