You probably have one or two rattling around in your garage or at the bottom of a knapsack: small books covering flora and fauna, how to identify and where to locate. In other words, field guides! I had no idea that there were so many field guides out there until I saw the International Field Guide site, which lists literally hundreds (thousands?) of them. It’s at http://www.library.uiuc.edu/bix/fieldguides/main.htm .
This site lists field guides in a number of categories, from plants to animals to astronomy to rocks. You can browse categories from the front page, or you can search. A full record search for trees found 552 results, from A Field Guide to the Acacias of Kenya to the simply-named Trees. Records contain author, title, publication details, description, region, and classification.
The database includes both titles that are in print and out of print, but unfortunately there’s no title link to Amazon, Google Books, or even WorldCat. If you find something here you want to follow up on — and I bet you will — you’ll have to go beyond the basic information this database offers. But what a fun browse! A tremendous amount of information in one place.