What to read after Hardy Rhododendron Species?

"An extensive introduction places the work in context as it examines the history of Rhododendron classification and gives a full survey of plant structure. Species are then listed in systematic order, so that similar species occur close to each other in the text. These are fully described, including complete citation of existing illustrations and notes on the occurrence of wild-origin specimens in cultivation. Each description is followed by a rigorously tested, easy-to-use diagnostic key. Further diagnostic information is provided by beautiful photographs that include close-ups of flower and leaf, as well as microscope images of leaf surfaces. Completing this failsafe handbook are lists of individual diagnostic characteristics and unique gardener's keys that will lead even nonspecialists to an accurate identification."--BOOK JACKET.