Thanks for all the suggestions!
My local library is pretty small. They are more than willing to get a book through interlibrary loan, if I have the title.
I also thought, if I had a couple good titles, I could download the ebook versions. Then I could take it into the woods with me on my iPod.
I have Michael Derr's big green book on woody plants, but it is not that useful for ID on trees in the woods. And, way to heavy to carry!
I was hoping there was a book that would tell about which characteristics to look for to tell the difference between trees... such as between silver maple and red maple. Like some bird books do. They will point to an identifying characteristic.