The main books about pterosaurs that I know of are:

The Illustrated Encyclopedia of Pterosaurs by Peter Wellnhofer, and

The Pterosaurs From Deep Time by David Unwin.

There's another book that will be released later this year by Mark Witton, one of the leading pterosaur experts: Pterosaurs: Natural History, Evolution, Anatomy.

Pterosaur.net is a good source of information as well, and was created by several paleontologists who study pterosaurs. Check the Origins and Relationships page for info on their evolution; unfortunately not too much is known yet, but that site explains what is and is not known.

Archosaur Musings is the blog of Dave Hone (another paleontologist) and has several posts about pterosaurs.

Edit: misspelled a name