Dave Marsh, Before I Get Old: The Story of the Who (1983)
First published in 1983 (and never revised), this book leaves more recent ground uncovered, but it still provides the best coverage of the band's origins and early years.
Pete Townshend, Lifehouse (1999)
Townshend continued to rework the playscript for his never-produced rock opera until 1999, when it was finally released.
Mark Wilkerson, Who Are You: The Life of Pete Townshend (2008)
Wilkerson adds new material in this latest edition of his biography of Townshend. Detailed, and in places even dense, the book explores events through 2007. Although focused on Townshend, it's a nice companion to Marsh's treatment of The Who's earlier years.