I highly recommend this book for improve the writing part of the exam. I got a 25 in this section and I am sure I owe 2 or 3 points to this book. I think I can write better now in English than in my own language (I am not good writing :) ) It provides good hints of what they expect.
Excellent pocket book, that will help anyone adding a nice touch to toefl exercises. Read it whenever you can and by the time you do the exam, you will notice a great improvement,in your writing habilities