The required textbook for the course is Introduction to the Theory of Computation by Michael Sipser, PWS, 1997.
That book does an excellent job with the material for at least the first 60% of the course. (One of the things it does an excellent job with is going over things somewhat lightly, so we can cover that material in only 60% of the course and move on to some more advanced material.)
There are two optional texts: