Java Enterprise in a Nutshell (http://www.amazon.com/Java-Enterprise-Nutshell-OReilly/dp/0596101422/sr=8-2/qid=1170860944/ref=pd_bbs_sr_2/104-7824034-5535953?ie=UTF8&s=books) gives (imo) a quite good overview about the single areas. Only drawback might be, that not as many frameworks as I would like to see, are mentioned in the book (e.g. not mentioning Spring).