From the back of the book:
"Spared from the ravages of the Clan invasion, the Free Worlds League flourished as an arms supplier to the embattled legions of the Inner Sphere. Captain-General Thomas Marik patiently guided the Free Worlds League Military through a long-overdue reformation as the troops of his Great House rivals battled the invaders. Bolstered by the League's powerful military-industrial complex, the FWLM now stands as one of the largest and best-equipped forces in the Inner Sphere.
This classified field manual, seized from the League's intelligence organization, reveals the inner workings of the FWLM, from the humble Marik Militia to the elite Knights of the Inner Sphere.
An invaluable resource for both allies and enemies of the League, the BattleTech Field Manual: Free Worlds League provides a complete survey of House Marik's military. The manual includes dossiers that describe the history, officers and tactics of all FWLM BattleMech regiments; special rules that reflect the unique capabilities of each regiment; new weapons, equipment, exclusive FWLM BattleMechs and more."