I purchased about 10 books from Amazon on abs in order to compare them. This one is fairly big, but there is a lot of white space on every page (you're paying for all of it). It also has confusing lay-out so that it's hard to use. If you're interested to know how it compares with other books, my conclusions are below...
If You Want to Trim Your Waistline: You can't trim your waistline without losing fat, and you can't lose fat around your waist without losing it everywhere (focusing on a muscle group like the abdominal muscles doesn't burn fat in that location, just a little bit of fat from everywhere on the body). So, if you want to trim your waistline, skip the ab workout books and go with a good, proven overall weight loss and fitness book like Bill Phillips' Body for Life. The Abs Diet is a similar program, but like all the Men's Health publications, it advertises a 6-week transformation, which is just a little unrealistic. Plan on more like 12-24 weeks to see really noticeable changes if you are fat.
If You Want Sculpted Six-Pack Abs: If you are overweight at all, see above--you can't get a six pack while you're overweight, and you can't lose abdominal fat by doing an ab workout, so go for overall fitness. However, if you are already lean, see below.
If You Want to Strengthen or Build Your Ab Muscles: If you're trying to improve for work, play, or rehab, you might consider the following books: The Body Sculpting Bible for Abs Deluxe DVD Edition contains decently up-to-date information and tells you exactly what to do and when to do it, based on a six-week fitness course. If you're looking for a similar book with more information, you can choose from The Complete Book of Abs or The Complete Book of Core Training. The Complete Book of Abs (1998) is a little out of date in terms of its dietary/nutritional recommendations, but it focuses more on exercises that develop the external abdominal muscles (the ones you see in a six-pack), including lots of variations on leg lifts, bicycle motion, and sit-ups. It will also give you more resources for creating your own program, and, if that's what you want to do, go with this one instead of The Body Sculpting Bible. The Complete Book of Core Training (2006) focuses more on the functional body core, including internal abdominal muscles, legs, etc., and includes more trendy exercises using medicine balls, exercise balls, yoga, etc. A different sort of book is Stronger Abs and Back (1997), which was written before the current fad of selling "core training," but contains the elements of core training because it gives good functional sports-focused advice. Its dietary recommendations are out of date, but it recommends a 24-week workout plan, which is much more realistic than the 6-week plans advocated by many of the other books.
If You Have Back Pain: See your doctor, and if he prescribes abdominal/core strengthening, see above.
My one-book recommendation: Body for Life.
My two-book recommendation: Body for Life + Stronger Abs and Back.
My three-book recommendation: Body for Life + Stronger Abs and Back + The Complete Book of Abs.
My four-book recommendation: Body for Life + Stronger Abs and Back + The Complete Book of Abs + The Abs Diet.
Hope this helps!!