William Montgomery, former US ambassador to Serbia and Croatia, has written a book "Struggling with Democratic Transition: After the cheering stops" about his period as ambassador. He tells some things about helping the opposition against Milosevic but it is obviously that this part of the book has been censored a bit by the State Department. He writes about close contacts between politicians and criminals like between Đinđić and Legija and between Jovanović and Spasojević. He is very negative about Carla del Ponte who he sees a bull in a china shop. He also mentions a meeting with Milosevic's wife who said that her husband would rather die than serve a prison sentence.
I am not certain where to buy the book outside the Balkans. It is not on Amazon.