Books: Basic information about searching for books
To limit your search to French language, use the Advanced Search option and click the Language box. Add French, and then fill in the rest of your search details (keywords, for example, or other limits).
Once you are looking at the search results page, you can also use the left column to limit by language.
Note that this language limit includes books with even just a little French content, even if the entire book is not written in French.
Hint for Esearch: because some French and English words have the same roots, you can search for both by using the catalog's truncation symbol, which is "*" For example, searching for democra* will find all the words with that root, such as democrat, democratic, democracy and also democratie. Searching for biling* will find bilingual, bilingualism, bilingue, etc. If you want only the French term, then spell it out completely (diacritics don't matter: you'll get the same result for poésie and poesie).