Joe Friel's The Cyclist's Training Bible

This is the go to book for bike racers who have hit their peak with just doing group rides and races as they come, and are ready to go further. 

It is based on periodization, which you must do to some degree to have any sort of success in racing. Recovery is what actually makes you strong.

I am not overly scientific in my training and often go by feel, but I have read this book numerous times and use the general ideas often. I'd say if you're serious about racing, this book is kinda a must read.