The Man Who Used the Universe — Alan Dean Foster

A notorious criminal pursues peace -- and power -- with alien enemies in this sci-fi novel from the #1 New York Timesâ€"bestselling author of The Damned Trilogy.
 
No one knows the true motives of Kees vaan Loo-Macklin. He's a mastermind criminal who gave up his place at the head of the dark underworld to become a legitimate member of Evenwaith's cities. But soon he was reaching out to powerful enemies -- -the slimy aliens called the Nuel. Loo-Macklin negotiates an illusory peace agreement and gains precious alien secrets in the process. Is he after peace, power or pure evil? With enemy starships beginning to amass, we won't have to wait long to find out.