Read The Love You Make, a Beatles' biography. It shows how Lennon was a violent juvenile delinquent and enjoyed mocking cripples and the deformed.
How reliable is it though? - I don't have a particularly high opinion of Lennon as a human being but it's well known the dead can't sue and people will write any old gubbins about them as a result. I read a particularly vindictive biography of a dead musician I admired much of which was debunked without refering to the vindictive biographer by a later biographer who had much more access to said musicians' inner circle but whose debunking of the said musicians' own myths said he wasn't writing without being afraid to critise.
I've studied history and you always have to bear in mind the possible biases and agendas of whoever writes about subject - always!!