If you are unfamiliar with a topic, it is often best to start with an encyclopedia, reference book or review article to gain a basic understanding of your topic as well as terminology used in the field.
Remember--books often have bibliographies that will lead to other sources.
If you have a specific species that you want to search (animal, plant, etc.) start with a OneSearch keyword search using the name of your species, and then if necessary, limit your search to one of the subjects listed.
Books are on the shelves according to subjects. Go to the Library of Congress for a detailed outline of categories/call numbers. Once you know the broad subject you can browse the shelves.
These books caught my attention; perhaps you will find them interesting as well.
Bread, Wine, Chocolate by 
The Diversity of Life by 
What Species Mean by 
