Elements of User Experience
Jesse James Garrett
http://www.jjg.net
http://www.amazon.com/exec/obidos/ASIN/0735712026/

Don't Make Me Think
Steve Krug
http://www.sensible.com/
http://www.amazon.com/exec/obidos/ASIN/0789723107/

Learning Ez Publish 3: Building Content Management Solutions
Paul Borgermans, Tony Wood, Paul Forsyth, Martin Bauer, Bjorn Dieding, Ben Firt
http://www.amazon.com/exec/obidos/ASIN/1904811019/

Information Architecture for the World Wide Web
Louis Rosenfeld, Peter Morville
http://www.amazon.com/exec/obidos/ASIN/0596000359/