One of my favorite authors if Richie Unterberger, who has written several excellent books on 60s music including books on the Beatles, Velvet Underground, the Who, etc.
Check out his work here:
URBAN SPACEMEN AND WAYFARING STRANGERS: Overlooked Innovators and Eccentric Visionaries of '60s Rock:
JINGLE JANGLE MORNING: Folk-Rock in the 1960s:
UNKNOWN LEGENDS of Rock'n'Roll [Updated & Expanded E-Book Edition]: Psychedelic Unknowns, Mad Geniuses, Punk Pioneers, & More:
WHITE LIGHT / WHITE HEAT:
THE UNRELEASED BEATLES: Music and Film:
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