First: This is a fine piece piece of work. Eckenwalder is known and respected throughout North America for his work with conifers, and has devoted many years to the preparation of this, his masterwork. The introductory chapters, accounting for 68 of 720 pages, are especially useful. The chapters on classification and names make a great primer on taxonomy for lay audiences. The chapters on habitat and morphology present excellent information, some of it never before published, on conifer botany. The bulk of the book, pages 69 to 631, addresses the families, genera, and species of conifers. Pretty good keys are presented to enable easy identification. The treatment of each taxon consists of two or three paragraphs that contain information needed for an accurate identification, followed by tidbits on subjects like ecology, uses, etc., but there is no systematic approach to this information. There are a few drawings and maps, many black-and-white photographs, and one section with 65 glossy color photos.
Second: Eckenwalder is a "lumper" and this volume identifies only 550 conifer species. This is 65 species less than in Farjon's superb A Handbook of the World's Conifers, and 100 species less than are recognized by many taxonomists. Each species is treated in rather cursory manner, and in general there is little information on any subject other than identification by means of morphology, which means that you don't actually learn much about these species - their ecology, their importance to people, and their evolution and history remain pretty much a secret. For this reason I am annoyed by the book's subtitle, "A Complete Reference;" it's just not true. I would have subtitled it "a guide to identification" because, for most taxa, that is this volume's primary strength. The black-and-white photographs are mostly not well reproduced and add little to the substance of the book, which is regrettable but probably helped to maintain a reasonable price.
In conclusion, I highly recommend this book for any one who is mainly interested in being able to identify the sort of trees that you are most likely to find in an arboretum. If you are interested in a general introduction to conifers as a group, you would be more happy with another Timber Press publication, A Natural History of Conifers. If you want to know more about the history, ecology, and uses of conifers, you are better off buying books about the species or region that interests you, or else coming up with the dough to purchase A Handbook of the World's Conifers, which addresses these subjects.