I've been collecting motorcycle magazines since 1972,.....way too many.
But in the last five years or so I've been collecting books, DVDs, and VHS tapes about all things relating to motorcycles.
One Christmas may wife gave me the four book set by our own Daniel Meyer (signed copies no less). I've got both the "Long Way Round" and "Long Way Down" documentary series. I've got historical reference books on "Board Track Racers", custom builders (Indian Larry, Arlen Ness and Billy Lane), and several english books on "Cafe Racers", "Rockers and Mods", but my personal favorites are by Sonny Barger.
One of the best is "Ridin' High, Livin' Free", a compilation of various stories and adventures by true entusiasdts (not just Hells Angels). Pick this one up and you'd have a hard time putting it down. Defenatly a "must read" if your a true entusiast.