For anyone interested in what's now called classic rock, I highly recommend Lilian Roxon's Rock Encyclopedia, published in 1969 and updated by Ed Naha in 1978--one of the first books to take rock music seriously. Roxon wrote well, and her taste was excellent. You can buy used copies from the usual online sellers. It's in demand, but there were a bunch printed, so you should be able to pick up a used copy for $10-20.