I have it, and I think it is good if you are a DBA, but not necessarily for Java or C++ Programmers who write code to connect to DB2. It has a lot of information I DON'T need, but not some things that I DO, need. For example, it will explain the concept of pooled data sources but does not tell you how to create them, connect to them in your code, etc.
It has a LOT of info regarding what has changed with UDB Version 8.
I use it mostly for looking up functions, syntax, and the error codes (on the front inside flap) mostly. I'm sure there are better references for programmers, not sure what.