The Hoffa Wars, by Dan Moldea, is a really good book about Hoffa and the mob, too. Mostly about rebels trying to reform the Teamsters, but it spares no details about Hoffa and the IBT's mob connections, from 1930's Detroit, to his fallout with Tony Pro, to currying favor with Galante in prison just before disappearing.

"...the successful annihilation of organized crime's subculture in America would rock the 'legitimate' world's foundation, which would ultimately force fundamental social changes and redistributions of wealth and power in this country. Meyer Lansky's dream was to bond the two worlds together so that one could not survive without the other." - Dan E. Moldea