There were only ever four people who knew the story behind the sacking of Pete Best. They were John, Paul, George and Brian Epstein. At the time, all were extremely reticent. Today, only Paul remains alive, and he isn't talking.
Spencer Leigh has, therefore, had to perform detective work, to piece together evidence pointing to the truth. .He has interviewed those closest to the events, as well as examining behaviour patterns within the group.
There were excuses for the sacking, and reasons for the sacking. The excuses are well known, for example, George Martin's decision to use a session drummer to replace Pete on "Love me Do" Ironically, of course, he also brought in a session drummer to replace Ringo].
The reasons are much harder to find, but Spencer puts it all out there. In my opinion, of the reasons discussed I believe that it was jealousy by Paul which was the underlying reason for the sacking. I have a good friend who was a Cavern doorman, and he told me "if there were ten girls hanging about waiting for the Beatles, eight of them would be waiting for Pete"
The Beatles are still, to me, the best group ever, but this was a shameful episode in their career. As such "Drummed Out" is an essential part of the Beatles story.