We have weekly readings from ACS and weekly lectures, so I read for these. Usually also involves reading on the subject from a surgery text (they gave us Sabiston). Also read before cases or when I make mistakes. I'm also halfway through Miller's and trying to get it done before CA1. I don't know how much I'm retaining, since I'm reading most of it on my nights, but it will at least be familiar.
I don't know what the prelim program you will be at is like, but the ICU book by Marino and Surgery Recall (in addition to whatever they want you to read) will help you early on. Perfect your knot-tying. Learn how to be proficient at placing lines. Understand basic patient care (fluids, electrolytes, postop care, wound care, etc). Read about procedures the night before. Know your patients. Take Step 3 earlier than later and that will help your knowledge as well.
Feel free to PM me if you have other questions. If you get to take electives, make sure you take a dedicated ICU month +/- ER, or whatever your advanced program recommends (this is what was recommended to me).