David Benzing is a botanist with a career-long researcher's knowledge of epiphytes. His book, Air Plants, presents as an advanced text for those already familiar with at least the basics of botany. Read with care, the book reveals the diversity and extent of this unique family of plants, replete with details on the variety of environments in which they may be found and the variety for forms that they take, including their nomenclature and biology. This makes for an excellent background work, but one challenging to anyone who is primarily interested in the practical care and breeding of epiphytic plants, such as the popular bromeliads and orchids. I have rated it high on the scale due to its informative nature, but caution some potential buyers to be aware that they are in for a challenging read.