If you're looking for Cisco Press books in particular, Safari Books is a great (legitimate) way to access any/all content you're looking for. It is subscription based, but well worth it in my opinion. Here's a link to the site:
http://www.safaribooksonline.com
Else, if you're primarily interested in configuration and technical guides, all of the documentation on Cisco.com for ASA and FWSM is VERY good.
Best,
Christopher