Warrior trilogy (En Guarde, Riposte and Coupe) for the story on the joining of House Davion and House Steiner with the marriage of Hanse Davion to Melissa Steiner as well as the 4th Succession War. A big event in the BT timeline.
Heir to the Dragon: A good look at the Draconis Combine and the story of Theodore Kurita's rise to power.
The Grey Death trilogy (Decision at Thunder Rift, Mercenary's Star and Price of Glory) some of the first BT novels and a look at one of the most famous mercenary units in the setting. Price of Glory also has the story of the discovery of the Helm Memory Core, which is what kickstarted the recovery of LosTech for the Inner Sphere after centuries of losing technical knowhow thanks to constant warfare and the efforts of ComStar to suppress any technological innovations or discoveries/rediscoveries.
Wolves on the Border. More insight into the Combine as well as Wolf's Dragoons and the reason for the conflict between the two.
The Camacho's Caballeros books (Close Quarters, one I can't remember the name of and Black Dragon). Like someone already said, pure fun.
Edited by Steinar Bergstol, 13 July 2012 - 02:09 AM.