Naturalist David Sibley, like Tory Peterson before him, made his reputation painting and annotating birds before expanding to other biological realms. Sibley’s guides to birds and bird behavior (recommended on Cool Tools) are the best all-around guides to the birds of North America. Sibley’s beats out Peterson’s, and the dozens of others published today. Sibley’s newest book, also written and illustrated by him, is the best all-around guide to the trees of North America, again displacing the many other field guides to trees in print.
Sibley’s illustrations are clear, crisp, and accurate. He manages to maintain distinctions in tree types where species get fuzzy, like in the oaks, or firs. His maps are specific. He includes more parts of the tree than most guides — buds, bark, branches, seeds, silhouettes, flowers, cones, etc. — which really help in identification. And he includes not only native trees but many feral varieties, and even widely planted ornamentals. One detail I appreciate: he lists alternative common names to trees, since trees seem to have local names.
With Sibley’s guide I’ve been able to identify more trees than with other guides. However the book is big, not at all pocketable, or the kind of thing you are likely to take with you into the field on a hike. Perhaps future editions might remedy this. I use this quality softcover edition (a delight to browse) by taking samples and photos outside and returning home to identify.