Hi, The book market is pretty immature still for portal/portlet development. If you cant find what you want from Amazon then you should still be able to find all the info your after on the web especially in places such as the Websphere Portal Zone (other resources link on main portal forum page). This info is still relevant even if your not a Websphere shop (lots of 168 and general stuff around development).
Ive got some other good resources which are on my machine at work. I'll post them when I go in Monday.
"Delivering systems from the glass to the arse!" [ June 17, 2006: Message edited by: Rob Doughty ]
Also at the top of this forum there is a link to the JSR Spec. Go there and get the Spec document. It is about 130 pages and is actually easy to read. JBoss Portal, a plug here, is really easy to use too, so you can just create Portlets and your mapping file and drop the war file into JBoss.
Here is a link to get the free Stefan Hepper book on portlets. Why read this thing? Because Hepper had a lot to do with JSR_168, and he was initially contracted to write a book about portlet development the JSR-168 way. The book is listed om amazon com as "Portlets and Apache Portals", by Stefan Hepper. My understanding is that the book is not in fact in print, hence, the pdf version from Manning. (It is very nice of Manning to allow people to download this for free, by the way. It may not stay that way for long).
Go to: http://manning.com/hepper/ You must scroll down to the bottom, open a Manning account if you don't have one (it's free) and then the link appears to the 11Mb pdf.