All of these test preparation books for the TOEFL exam are super expensive. Therefore, I'm going to provide my personal assessment as to which of these books are really useful so that you can study for the speaking section more efficiently and inexpensively.
Try to get your TOEFL books from ebay or amazon - I have most of the TOEFL books which have been published and got them at huge discounts (or students whom I helped to pass the exam gave them to me).
THE BEST BOOK FOR THE TOEFL SPEAKING EXAM
Hackers Actual Test Speaking contains 12 practice speaking tests and 1 warm-up speaking test. For the most part, all 6 questions follow the actual format of the real TOEFL exam (with just a few exceptions). This company did a great job for students trying to pass the speaking section. Kudos to Hackers. You made my job as a TOEFL teacher much easier with this great test prep book - some of my students have scored in the high 20s and even reached 30 with the help of this book.
This book gives you 5 complete speaking tests which were actually administered in the past. With Hackers and this book, you'll have 18 practice speaking tests.
This book provides 2 complete speaking tests and about 150 independent writing topics, which can be used as TOEFL speaking questions for question number 1 or 2. The independent writing topic seems to follow the format of TOEFL speaking question 1 or 2. So if you buy Hackers, the previous book and this book you'll now have 20 complete speaking tests and over 150 number 1 or 2 questions to work with.
This book has numerous TOEFL speaking questions but questions 4 and 6 in this book do not always follow the format of the actual TOEFL exam. It would be an ok book for questions 1,2,3,5 - but be careful because it seems that sometimes the number 5 questions can deviate from the format a bit. Interestingly, if you have a good tutor (like me :P) he/she can play around with the scripts that this book provides so that the material can be made to fit the actual test format. For example:
Again, 1,2,3,5 often seem ok, but 4 and 6 don't always follow the actual test format.
Yet again, 1,2,3,5 are mostly OK, but questions 4 and 6 regularly seem to deviate from the actual test's format.
I hope this helps! Drop me a line at firstname.lastname@example.org if you have any questions or want to recommend a good text for the TOEFL speaking section.