To date:

Al Capone by John Kobler, Mr Capone by Robert J Schoenberg, and The Mafia And The Machine by Frank R Hayde.

Hayde's is a slime 190+ book, but it moves at a blistering pace and sets the record straight on Pendergast and his political machine, his mob and political ties including a farmer cum President of the United States Harry S Truman, Kansas City Mafia aka the KC Outfit and it's front men Johnny Lazia and Charlie Binaggio; mobsters Joseph "Scarface" DiGiovanni, James Balestrere, Tano Lococo, Tony Gizzo and the Civellas - "Uncle Nick," "Carl the Cork" and "Tony Ripe", and William "Willie Rat" Dominick Cammisano Sr.

The Union Station Massacre, River Quay War with the Bonadonnas and Speros brothers, the Strawman case (one of the source inspirations for Scorsese's Casino), etc. I hope KC native Frank R Hayde continues to write more on the KC underworld.

Worst: well after reading both the Kobler and Schoenberg biographies Jonathan Eig's book is tripe.