wrote about Alan Chu's wonderful Photographic Moon Book in 2007. It is an observer's photographic guidebook to the Moon containing nearly 300 annotated images of lunar features as well as some great introductory material on the Moon. Alan has continued to update and improve it. He released version 3.5 in March 2011. It's a free PDF, and it's big - 125 MB. You can download it from Alan's own Hong Kong site, or from a US based mirror site.
When I first found this in 2007, there was also a smaller document called the "Moon Science Primer." Most of this material is in the introductory section of the Moon Book, but the Primer goes a little deeper on some topics. Although Google still has a link to this, there is no link on Alan's home page, and the Google link returns a "not found."