If there was one video game I've enjoyed playing the most, it'd probably be Mechwarrior 2. While I might've played Diablo II more, I really think Mechwarrior 2 is the one I had the most fun with. As such, I've always had a love of Battletech stuff. Though, sad to say, I've never actually played the tabletop game, itself. I did a brief stint with the Dark Age version that WizKids put out. I really should look into the game more. And Catalyst Game Labs is here to help with some new Technical readouts.
And since I did play the WizKids game, and knew a bit more about that timeline, these two books would seem somewhat familiar to me. These two books add in new equipment, vehicles, aircraft, weapons, and, of course, mechs, to the lexicon of Battletech. There are also new variants and pilot profiles you can use to enhance your game with.
You can get the pdf version of the books now, or pre-order the print versions. If you order both together, they've even got a special deal going on.