The textbook for this class is Speech and Language Processing by Daniel Jurafsky and James H. Martin.
Note we'll be using the 2nd edition released in 2009. It should be in the bookstore. The 1st edition is not an acceptable substitute.
You're welcome to purchase the book anywhere you like. But you are responsible for having the book when the semester starts. Note that last year, many students who ordered the 2nd edition received the 1st edition from various no-name websites. Caveat emptor.