I had the same problem with the 200-602 exam; it's a VERY broad exam that asks for details about every aspect of computing. These A+ certifications are some of the most comprehensive that I've ever had to take!
Along with all of my other materials, I use three or four A+ books when doing research for my training course. One that I keep coming back to is:
Mike Meyer's A+ Certification All-in-One Exam Guide
It's written with a great "voice," and the content is some of the best that you'll find in any technical book, A+ certification or otherwise. Mike has a great knack for taking very technical topics and explaining them in real-world terms that anyone can understand.