Check out your county extension agent or University. Ohio State has one I use all the time when trying to figure out what grows around here (I live in SW Ohio).
For books, "Handbook of woody plants" by Michael Dirr was used as a text book in my brother's college classes. Very descriptive and a great source for varieties of a type of plant (For example, the author seems to like a Shirobana Spirea more than an Abbotswood Spirea.