I was PPL and did it with the Aviation Theory Centre "Command Instument Rating" book.
As you do each chapter do the test at the end faithfully, re-read the chapter and redo the test until you get an OK mark. If you struggle on any issue, discuss with a rated pilot or an instructor - should not need to do this much however. When you can pass the trial exam at the end then sit for IREX. I passed first go.
Having said that, it's a solid, searching exam and requires serious study effort (or it did for me).
Last edited by bentleg; 16th April 2011 at 06:21.