Book Search
A book search feature should already be installed on your site when you first begin to use it. Normally it is located in one of the sidebars on the left or right side of the screen and will have a single field that can be used to search for keywords used anywhere in a book entry.
If you want to search with more specific criteria (author, title, year etc.) you can click the Advanced search link, which will take you to a more detailed search form.