If you are new to Unix and AIX, I would recommend just getting a basic book on AIX so that you learn the basics of the Unix shell, Unix file systems & file permissions, and the administrative tools available to you on the platform. I don't have my books handy but about any book on general AIX should be fine.

Another book you might want to look at afterwards isn't specifically geared towards AIX but Unix systems in general. The book is "Oracle8 and Unix Performance Tuning" by Ahmed Alomari. This is a fantastic book for tuning Oracle on UNIX. You'll need to be familiar w/ the basics of Unix before you tackle this though.

Other than that, make sure that you read the System Administration, Concepts, and Tuning guides that Oracle supplies with the DBMS. The installation guide will be very important as it discusses the specifics of Oracle on the platform you are running on. I seldom hear people talk about the excellent manuals that Oracle supplies which is suprising because they are both well written and are "from the horses mouth". I would highly suggest becoming familiar with these before you spend money on additional texts for Oracle.

Joe