Let me tell you: if you have to pick just one book as a reference on woody plants for the garden, it most definitely should be Michael Dirr's "Manual of Woody Landscape Plants: Their Identification, Ornamental Characteristics, Culture, Propagation and Uses." There is nothing else that comes close. No, it doesn't have pictures, but who needs them when you can easily do a google search of images. What it does have is everything you need to know about every woody plant you are likely to encounter.
Where it particularly shines is in his observations on 'landscape value.' I don't think I have ever taken issue with any of his comments, which range from "a sickly sight in any landscape" (for corkscrew willow) to "one of the best small specimen trees I know" (for one of my favorites, Parrotia persica). It's also quite comprehensive -- for example, he describes 38 species of maple in the fourth edition, most all of which deserve a place in the Michigan landscape and most all of which are quite available.
It's a fun read. It's the book you'll see on the sales counter at Abbott's Nursery. And it's the first reference I turn to when I'm looking for a second opinion on the ornamental value of woody plants.