This is a great book, with every tune arranged two ways: One for the beginner (that's me) and one for advanced players. I like to learn the easy version of each tune and then try the more difficult one afterward.
Even though I can't yet play most of the advanced stuff, I have fun trying it out and I am constantly learning - I can go back and forth between the two versions, incorporating additional harmonies or rhythms as I am able to pick them out, which helps me gain a more in-depth knowledge of the instrument and the music. Furthermore, the easy arrangements do not stray too far beyond the 29 strings of my folk harp.
I also recommend Sylvia Woods' book of Christmas music, which is set up the same way and kept me happily occupied throughout this year's holiday season.