Captain Hook,
Check out:
The Complete Guide to EKGs (by O'Keefe)
and
ECGS for the Emergency Physician (by Mattu et al.)
These two books are for EKG reading practice and are just pages of different EKG's with the explanations and offical reads listed in the back. They assume that you have already read a book like Dubin's or "The Only EKG Book that You'll Ever Need" and have the basic knowledge.