One of my favorite music theory and notation books is Elementary Rudiments of Music by Barbara Wharram. It's pretty rigorous, and you get quite a bit of notation practice while you take in the theory, but the rigor is well-paced and worth it. I'd never absorbed so much theory so quickly as when I was working with this book. It's mostly a work book than a reference, so my 9-year old copy is pretty worn and full of pencil markings. I'm looking to order a new copy: Amazon can special order it, but Tapestry Music has it [wrong cover on that page, but the right book] as well as the answer key, which is probably worth having.