From the back of the book:
For Players:
Expanded character creation rules that compile and update all Field Manual life paths and explain how to create your own. Also included are an alternate point-based character creation system and a complete construction system for battle armor.
For Gamemasters:
Provides expanded rules on how to run adventures in the Battletech Universe, how to incorporate contact and enemies in your game, as well as a section on the various underworld organizations in extent. Also includes a complete section on creating and using creatures, with ans ample sampling of alien fauna.
The Classic Bttletech companion offers advanced and alternate rules for players and gamemasters. This indispensable books provides numerous new skills and traits, advanced weather rules, administration and organization of noble land-holds and more information of the life in the Mechwarrior universe.