I tried the approach you're asking about, just using the kalm prep software and would not recommend it. The software is good, but there was stuff on the test that was not in the prep software. There is a study guide on the caia site. I would buy the books and go through the study guide reviewing anything you're weak on. I was surprised I passed after the way I felt leaving the exam.
I think for the prep software that there may just not be enough historical tests yet to cover the full spectrum of available topics. They have also made minor modifications to the curriculum along the way. I would only use it in conjunction with the suggested reading list.
It's a fairly tough test. The only other thing close I've taken is the 7, which was a walk in the park compared.
Also make sure you are comfortable with a financial calculator as it will help you move through the exam much more efficiently.