This A-Z guide to lesbians and lesbianism in the movies contains reviews, gossip, facts and commentary on over 200 films, including specifically lesbian films such as "Go Fish" and "Desert Hearts" as well as films with a lesbian character or theme, like "The Children's Hour" and "The Hunger".
This is a surprisingly complete guide to lesbians in films of the 20th century, which includes a lot of obscure films and contains reviews alerting readers to either unknown gems or (alas) the extremely poor production values one sometimes finds in LGBT cinema of this era.
Alas, this book is somewhat dated and reflects the prejudices of its era, specifically in regards to bi and trans issues. For example, it slates the film She Must Be Seeing Things partly because one of the leads is bi. The author of the review claims that because the bi lead snogs a man, this implies that all lesbians want to snog men. The guide also falls a bit flat on art films, which also contributed to negative review of this film.
However, if you want to know which 20th century non-art films about monosexual lesbians are worth watching, this guide is really handy.