Red Hood - Lost Days TPB
 

I just finished reading this one, and it was awesome! It explains what Jason Todd did training-wise to become such a bad ass. Check it out.

I will check it out. Has it been retconned out?

Retconned is a harsh way to put it, but I would say that some of the facts and the events in this TPB overlap stuff from Under the Red Hood. I picked it up for $6 at a Borders since they're going out of business.