I have to agree with the resident above me. For your own interest and your cardiology block in the future, Dubin is a good resource. It is not very in-depth, but it does a good job at teaching you how to interpret EKGs step by step. Everyone does this their own way, but Dubin does a good job. His book is a fill-in-the-blank format throughout which makes sure you're actively reading. Not only does it teach you how to interpret EKGs, it does a good job of teaching the basic cardiac electrophysiology and theory behind how EKGs work. All of that theory will be tested in the future when you're sitting in a cardiology exam.
What you'll need to know as an EKG tech will take you a far way now and probably as a medical student. Some gross abnormalities you can't turn a blind eye to, but other things are easy to miss. Just don't get stressed out. I know you're only in college, but take my cardiology professor's words to heart, "Don't stress out over these things. You have an advanced education. They pay people out of high school to interpret these things. Are you smarter than a HS grad? I sure hope so."
Edit: I see you're going to be a monitor tech and not an EKG Tech, but if you're still interested take my advice.