I found each section quite helpful. In reading and listening comprehension, the tips are especially helpful to those you can work if you do not know an answer once.
The speech lesson I find very helpful if you tend to be nervous. You can see the beginnings of sentences and vocabulary learned and prepare myself, which was very helpful for me in case of nervousness and the time pressure during the test.
The writing lesson is very helpful if you are not practiced indoors to write an essay in English. Otherwise, much repetition of the school year. But it is quite a very good repetition. Especially if you were no longer in school already a few years.
Overall, I found that the book has me very well vorberietet. A minus point gets it, because the right TOEFEL test yet slightly heavier than the texts in the book. In the book I had answered the question about 95% richitg, today the test I had a lot more problems.
That's the only point that you should keep in mind when working with the book. However, the question types and text types are very well run away and given lots of useful advice, which is why the book is highly recommended.