This is a comprehensive account of all known types of animal eyes. Taking diversity of optical mechanisms as a framework, it also discusses aspects of structure and function of eyes, including visual ecology, design philosophy, properties of light critical to vision, factors in eye adaptation and capabilities of a wide variety of eye types.
Full disclosure, I have an advanced degree in optics, so this book is right up my alley.
This book is chock full of information you likely can't find anywhere else. It's not exactly readable, but reading in snippets here and there across the year proved to be doable. Tons of fascinating info you'll find no where on Wikipedia.