Lyle Books
I have all three Ritz books, I got the "Lite" only a couple of months ago. The other two I got very early on in my love of uke. The Chord Solos book was very daunting, but the jazz book was a bit easier to get started in. I really was motivated to learn some strum/picking jazz stuff and surprisingly enough, I got familiar and more comfortable with it rather quickly. That is not to say that I'm great at it, but I would say that all three books will repay over a long period of time: for study, for learning, for motivation. And with the CDs that come along with each book, you have terrific audial examples to get familiar with.
HTH,
Craig