Thanks guys. It looks like Four Star is widely recommended and your other recommendations are appreciated too cjp_piano.
I have one more question though, do you think it is redundant to be working through multiple sight reading books? Is it much more beneficial to do Paul Harris level 1 and then Four Star level 1 and then Paul Harris level 2 and Four Star level 2 and so on..? And if that is a good idea do you think it would be a good idea to add a third book into the cycle as well?
For some background, I'm an adult learning without a teacher and I want to learn to sight-read music very well!
Thanks!