THese are the books with the rules, I'm using:
DriveThruRPG.com - Catalyst Game Labs - Battletech - The Largest RPG Download Store!
The main books are Total Warfare (Not shown in this list), Tactical and Stategic Operations, and Campaign Operation (just released, which had the rules for building a unit, contracts and the like)
I'll leave it open for another 24 hours.