Rating: 
Summary: Very formal and complete. Not very friendly sometimes.
Review: (I'm talking about the FIRST EDITION of this book)
This book is a must for any student or professor in the field. I've heard the new edition is more readable but hides some minor details from you.
I can say some paragraphs could have been written in a friendlier way, but in a general sense the book is a bible in its topic.
Rating: 
Summary: A must have for any student of computer science.
Review: A classic text on the subject and a must have for any student of computer science. If you have taken a course in discrete math as taught by most CS departments then this book should pose no overwhelming challenges. It also makes a great companion to Aho, Sethi and Ullman's "Dragon" book.
Rating:
Summary: A book for computer scientists
Review: A predecessor of the book was published in 1969 titled "Formal Languages and Their Relation to Automata." It was re-written in 1979. This is a classical textbook for last year undergraduate students or postgraduate students in computer science, especially those who are going to deal with computer languages, artificial intellegence, compiler design, computational complexity and so on. One of the author, J. E. Hopcroft, is the Turing Award winner of 1987.I have both versions of the book and I'd like recommend every computer science student spend some time on reading it.
Rating: 
Summary: Very Dissapointing
Review: After Having finished reading this book I found myself asking more questions than I felt were answered for me. From a pedagogical point of view this book leaves much to be desire. At times it is out and out confusing and seemingly contradictory. I am told this is supposed to be a classic: such a shame!
Rating:
Summary: Could be better
Review: As a student using this book, I simply found it a little too difficult at times to grasp what the concepts were. The examples, at times were just too complicated, and could have been done better with easy to understand examples. Not so sure about this one. However, if you are already tamed in automata theory concepts, I'm sure you'll love it.
Rating:
Summary: Could be better
Review: As a student using this book, I simply found it a little too difficult at times to grasp what the concepts were. The examples, at times were just too complicated, and could have been done better with easy to understand examples. Not so sure about this one. However, if you are already tamed in automata theory concepts, I'm sure you'll love it.
Rating:
Summary: Easier to understand, but not as completed as the first.
Review: Having studied the Formal Language and Automata Theory (FLAT) using the first edition of the text, I think this 2nd edition is much easier to read and to understand. This is a very good thing because the 1st edition was a bit difficult to follow, especially for those who aren't familiar with the subject already. (As stated in the preface of the 2nd ed. that the 1st was written for graduate students who already have the idea of what the subject is all about). Also, I found the approach "Example->Informal Def->Formal Def->Proof" very good, and should be used in more textbook. This way, the readers will have the idea of what they're going to study, what for, and why, instead of pointlessly studying something, forget it, and realize how important it is later (this happened to a lot of people, though). A lot of useful and interesting Theorems were also introduced. However, there're things missing in this edition. For example, the Greibach Normal Form (GNF) for the Context-Free Grammars, which was covered in the 1st edition. I'd talked to the professor who taught the FLAT class I took, and he doesn't seem to like this edition either. He said something like, it is of course easier to understand, but something had been left out. So, he still prefered the 1st edition. (Well, he is a very good researcher in Computation Theory and is now writing a book on Term Rewriting System, another model of computation, which will be published by Springer-Verlag. Don't know when, though. So, this edition is probably too easy for him :-) I, on the other hand, think that this 2nd edition is good on its own ground. It made the subject of Computation Theory easier and more accessible to wider range of people. (You still have to "think" and have Math knowledge anyway). Also check out Michael Sipser's book on Computation Theory. I think that one is somewhat better than this one. It uses lesser Math (don't get me wrong, I like Math), and clearer explanations.
Also look for the first edition in Library, used book stores, or wherever you can. That one is definitely a classic, and cannot be replaced by the 2nd edition. I agree with one reviewer here, so bad that this was a new edition, rather than a new book....
Rating:
Summary: A very good book for theory of computing
Review: Hopcroft's book is a very good introduction to the theory of computing, from finite automata to undecidability. He introduces the text with a crash course in proofs, which is useful for a text of this nature. They have several examples with illustrations to facilitate quicker learning of deterministic finite automata, pushdown automata, and Turing machines. These illustrations proved very helpful for me, a visual learner. The book itself is chock full of examples and theorems with proofs. Problems with the book: more explanation on Homomorphisms would be nice. The exercises can get very much harder than the simple material the book teaches, so running through them takes considerable amount of time often. Overall it's a good book, and a lot easier to understand than their first edition in 1979. The material can at times seem a bit outdated since the computing world has changed by several orders of magnitude since their original work, but it still provides a solid foundation in the philosophy and mathematics of computing. Perhaps if you're a Cornell student you'll get the privilege of taking this theory class with Hopcroft as your instructor; he's very nice and willing to help students understand the material.
Rating:
Summary: A very good book for theory of computing
Review: Hopcroft's book is a very good introduction to the theory of computing, from finite automata to undecidability. He introduces the text with a crash course in proofs, which is useful for a text of this nature. They have several examples with illustrations to facilitate quicker learning of deterministic finite automata, pushdown automata, and Turing machines. These illustrations proved very helpful for me, a visual learner. The book itself is chock full of examples and theorems with proofs. Problems with the book: more explanation on Homomorphisms would be nice. The exercises can get very much harder than the simple material the book teaches, so running through them takes considerable amount of time often. Overall it's a good book, and a lot easier to understand than their first edition in 1979. The material can at times seem a bit outdated since the computing world has changed by several orders of magnitude since their original work, but it still provides a solid foundation in the philosophy and mathematics of computing. Perhaps if you're a Cornell student you'll get the privilege of taking this theory class with Hopcroft as your instructor; he's very nice and willing to help students understand the material.
Rating:
Summary: Great Book !
Review: I like the "informal, then formal" way. There a few books that keep an eye on explaining everything in such a great detail, keep an eye on introducing everything step - by - step. I think, this is the way scientific books for non-experts, that like to become experts, should be written. Although my mathematical background is very bad, I had no problems reading this book. I prefer more pages for one conclusion (with examples and good explanation) than the Theorem -> proof -> conclusion scheme found unfortunately in many books. This book can be read like a novella! Keep up the good work: HOPCROFT / ULLMAN / MOTWANI THIS BOOK IS EXCELLENT !!!
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