If you go to the CompTIA A+ website
you can see the Exam Objectives after entering in some of your information. You can then do A LOT of your own research and learning through Google. Remember, Google is your friend, you can ask it anything and get answers 100% of the time.
With that said, buying some sort of Guide like you linked to would surely help, it really depends on your learning style. I learn best from searching on how to do things on Youtube, seriously! ...because I'm a visual learner.
Also, you may want to Google CompTIA A+ schools in your area. I plan to attend a series of courses(schooling) that will give me hands on learning for me to pass the A+ Certification Tests. The cost for that at the nearest school is $3000 with finincial aid available, and the tests are about $200 each. (There are two tests). The particular school I'll be attending is solely dedicated at teaching for these kinds of courses... it's not just a community college or some B rate place. There are practice tests on the CompTIA website as well... I was told you need a 75% or better on the final tests to obtain the A+ Cert.
I hope that helps.
EDIT: One of the best things I ever did to get me started was spend $90 on a van load of old computer junk in which I was able to get my first non-working computer to boot!, and sold tons of it on Craigslist which forced me to research the things I sold which in turn helped me learn about computer stuff. Also, I stuck around here and ASKED TONS OF QUESTIONS and read all kinds of threads. Jumping in on trying to fix some old computers like you have should really help and get you motivated to learn more.
Edited by Ferrari, 23 January 2010 - 05:20 PM.