Hi Megan.
The additional books are not required, though of course IAAP does recommend them. Honestly, there's no two ways about it, the test requires a mix of real world experience and old school style education. You may be able to find some alternatives that would work for you better, such as youtube videos, but one way or the other, you need to learn the concepts covered in the body of knowledge.
As an fyi, I'm offering some free webinars in mid-May through early June on Certification Options for Administrative Professionals. I go through several major certifications for admins and discuss what's involved, the costs, what prep should be done, recertification requirements, etc. Keep an eye on this forum, as I'll post registration info in a few weeks.
As my colleagues graciously indicated, I do offer a CAP study group. If you are interested in learning more about that, you can drop me an email at iaap@mrhenterprises.com.
Marie