Of the essay books, this does rank among the best in most categories. The advice is well thought out and gives you not only samples of prose but things to consider from the school's point of view. Items like word choice and essay style are also considered in detail.
As one of the other reviewers mentioned, most essays are unfortunately rediculous in length. If the essays could be infinite in length (as they are for basically only one top-25 school I can think of), these essays and the detail provided in them would be dead on. Once you begin writing however, you will realize that some of the detailed advice given and the rubrics to follow will quickly consume the 1-2 page limit and you'll need to start over and refine or completely rewrite. Use the essays for guidelines but be careful of all the prosaic fluff that the author recommends you put into your essay to create good "stories", sometimes using several double spaced pages just to set up a backstory in an essay-useless when you have only 2 pages to answer 3 subquestions!
The author spends alot of time saying, "Do X" and then within the same few pages or within the book will say, "Be careful of X," constraining you into an impossible writing situation. He will also do the opposite where he will scare you into the need to write too much by saying things like, "Make sure you talk about this aspect of your career. But don't forget this. And don't forget this. Oh yeah, and don't forget..." Again, if you have the common sense to get into business school, this book should be an inspirational outline more than the be-all-end-all of essay writing. The author should take care to give more examples of shorter essays which most top 25 schools want.
My advice: If you are looking to study multiple books, put this one on your list. If you are looking for one really great book, this may not be it (though I strongly advise you against using only one book.)