Harmony and Theory by Musicians Institute.
Trust me. It starts from the most basic and explains in layman's terms everything you need to know about basic theory and harmony. You can even download it on Soulseek or Emule if you want. My guitar teacher teaches at music academies and conservatories and he told me to get it to help with my instruction, and we go over it together.
I've got the Guitar Grimoire, but it's just basically a book of every scale and mode known to man without much instruction. I mean, there's a LITTLE at the beginning, but it's basically a practice book, not instruction.