I purchased this book while on a trip to England. This is my "go-to" reference book for taking along to the nursery or when ordering plants online. It is small enough to throw in my purse (4"x5"x1"), is organized according to Season, then Color, so it is particularly handy in coordinating year-long interest when designing a garden. The drawback for U.S. gardeners is that this book is written for a British audience (RHS in the title stands for Royal Horticultural Society), therefore I think that it would best be used in USDA zones 7 - 9. Regardless, I like this book very much and use it often.