Here are my recommendations, based on what I've read (4th year med student)
Basic Ophthalmology for Medical Students and Primary Care Residents, 8th Edition is a good starter... find it at the (AAO) Academy bookstore. You can read it in a weekend, and it's loaded with practical basic ophtho information.
Ophthalmology (Student Edition) by Yanoff & Duker. It's like a "Harrison's for Ophtho". It has everything from genetics to surgery. I love this book. I've heard that Clinical Ophthalmology by Kanski is very similar.
The Atlas of Clinical Ophthalmology by Spalton is very helpful to look at during your ophtho rotation/s, to know what to look for. There are very helpful diagrams next to each photo that point out the pathology.
These books are no small investment, of time or money, but I think they're worth it.