I love biology. This is a 40 page review on the evolution of vision. There is incredible amount of information here in this article. It is also very easy to understand with very little biology background. So, if you are worried that you don't know much biology, don't be afraid. It is very easy to understand and very well written.
Due to my new busy lab life, it took me ~1 month to read it, but it's worth. I highlighted tens of parts so that I can use them as reference even when I am talking to my "non-science" friends. I think this is an article that every person should read as a course material in some kind of elective course. The article tells you everything you would ever want to know about the evolution of vision. It is also open access!