I just skimmed through this ebook and it was very easy to follow. There's a lot of good info in here in a very short space but without being hard to follow or hard to use.
It includes a bunch of chord diagrams at the end as a sort of cheat-sheet and also has a little bit of homework (to make sure you really 'get' the concepts in the book).
It's free to distribute so I'm distributing it here, freely ?
Click here to download.