I stumbled across this book more than a year ago and had to have it. Although not an exhaustive reference book, it does cover a fair bit of ground. The pictures of the plants are lovely and most show the plants in a setting, which is helpful for seeing scale. Also, the plants are described in general (as genera) with a focus (naturally) on the larger specimens. Zone ranges, height and width, amount of prefered light, and season of bloom or foliage interest are also given.
I dicovered a good many plants in this book, thought twice about a few plants I had wanted to try (for which I'm thankful), and found good info on what I could do to improve the lot of the plants I already had that I read about in this book.
The name of the book describes perfectly the contents - all the plant are 5 ft or above for the gardener that wants some really BIG (GIANT) impact in their garden, it is a good reference book with tips and suggestions for plants in different areas.