It's been ages since I saw the movie but I gather from what I've read the two differences between this and the final film were this had more scenes involving Scylla at the beginning and alsouo the ending was different. In Goldman's account Babe meets Szell takes him out to the lake and shoots him. This version I read may have been the one with some Robert Towne doctoring because Szell seems to cut himself here... or is he shot? I wasn't sure. He doesn't eat the diamonds though.
Never mind, you can still tell it's mostly Goldman - page turning, gripping stuff with this bleak nihilistic tone. Babe really goes through the wringer: his professor doesn't like this thesis, he gets mugged, his girlfriend is a spy, his brother is a spy, he gets tortured by Szell, Janeway pretends to be his friend and betrays him. But he is a good runner and has a handy gun and those things turn out to save his life.
I never quite believed the scene where Babe blew away three toughs, crack shot or not, but the twists are great: Elsa is spying on Babe, Babe is Doc's brother, Babe is killed, Janeway is a traitor.
Goldman's New York feels like a horrible place, with its road rage, airport baggage chaos, bullying crims, muggers, corrupt officers, sweltering heat. Adds to the intensity of the piece.
The best character is Scylla, torn, broken, loves his brother... though some of his "we're too old for this" spy dialogue is clunky.
This is one of Goldman's best works but be warned, it is a bit depressing, with its torture and hero losing everyone close to him.