All-In-One CompTIA A+ Certification Exam Guide by Michael Meyers, Scott Jernigan (2003, Package)

Be warned, this book is not a quick crib sheet! There's well over 1000 pages here, covering every aspect of both the hardware and the OS exams. If you've left all your studying to the last minute, this won't help.

But - if you've decided that you truly want to understand the material, and aim for a really good score on the A+ tests, then this is an absolutely invaluable book. My partner used it for his exam, and scored well above average. I learned quite a bit too! It also comes with a CD in the back, although it was missing from the copy I bought, so I can't vouch for the content.

It's also a good book even for casual readers, although some of the material the tests cover is really quite old (I thought manual setup of IRQs died out with DOS?)

Don't be alarmed by the age of the book (2003) - last time I checked (2006!), all the material was still relevant to the current A+ exam. It's also the only really complete reference guide out there, as far as I know.