I had been into classical literature for a while but was at a loss as to which works I needed to worry about, and which were perhaps of lesser importance. (I never studied literature or classics at university.)
This book is a fantastic overview of the subject, divided by genre (e.g. epic, drama, rhetoric, history, etc) and chronologically within that. It is not a dictionary, but is a readable discourse on the subject, not at all stuffy. It also has an excellent suggested further reading list at the back. The time period covered is roughtly 700 B.C. to 400 A.D.
I think helps to have read at least a sample of the works that Dr. Rutherford talks about, but I certainly haven't read them all, and am really enjoying the book. Excellent reading for the armchair classicist!