First of all, let's set the record straight. The GMAT essays are not terribly important. Sure you don't want to bomb them, as they will be seen by the admissions office at the schools you're applying to. On the other hand, they're typically not given nearly the weight that your GMAT score is given. However, if you are nervous about them and want to increase your chances of doing well, you'll want to pick up this book from Arco.
The GMAT essay topics are not exactly a well-kept secret. In fact, in the back of the Official Guide to the GMAT, there is a comprehensive list of actual essay questions you'll see on the GMAT.
This book takes it one step farther by giving you an example of a well-written essay for each of the published essay questions. While reading these won't guarantee that you'll write a perfect essay, they should help you to get a feel for what the graders are looking for. Whatever you do, don't try to memorize the answers! We can't think of a bigger waste of time...
