To date the ones I've read and enjoyed are:
The Greatest. Which is about who else... Muhammad Ali
American Son by Oscar De La Hoya
Fire and Fear by Jose Torres which about Mike Tyson
Blood Season. Another Mike Tyson book
The Black Lights: Inside the World of Professional Boxing
Unforgivable Blackness: The Rise and Fall of Jack Johnson by Geoffrey C. Ward
I haven't read these books in YEARS but the one I enjoyed the most was the Black Lights because it really goes into how boxing politics worked in the 80's when King and Arum ran the show. It talks about how boxer Billy Costello (RIP) was trying to make it in boxing with all the politics that came with it.