I bought this book in a desperate attempt to pass a Theory of Computation course in which I was enrolled. I was stuck in the sad situation of having a non-English speaking, difficult to understand professor. In addition, the required text for the course was awful. Thanks to Sipser's book, I not only avoided dropping the course, but managed to get an A. (I'm not exagerating). Sipser's book is fantastic compared to others on the subject. It is written in easy to understand, plain, no-nonsense language. (Even the section on pumping lemma is understandable) I became aware of Sipser's book as a result of reading a customer's negative review of another (more expensive) book (Intro to Languages & theory of Computation by J. Martin) on the same subject. The reviewer suggested buying this book by Sipser instead, and that advice was excellent. (Many thanks to that reader, whoever you are!) If you are considering heading for the drop course line at the registrar's office, try this book before you give up and quit!