General books about forensics
Principles and Practice of Criminalistics: The Profession of Forensic Science, by Keith Inman and Norah Rudin. (Highly recommended).
Books about computer forensics
File System Forensic Analysis , by Brian Carrier, Addision-Wesley, 2005. (Highly recommended).
Forensic Discovery, by Dan Farmer and Wietse Venema, Addison-Wesley, 2004.
Digital Evidence and Computer Crime, by Eoghan Casey, Academic Press, 2004.
Incident Response & Computer Forensics Second Edition , by Kevin Mandia, Chris Prosise & Matt Pepe.