I met William Goldman up at Tannens shop one day. I was about 16 I think (really can't recall exactly). He was looking for someone who would explain tricks to him and one of the demonstrators suggested he talk to me. It was my impression that he had approached some others and found that they didn't want to explain how stuff worked since he was a layman.
I had no idea who he was--his name didn't mean a thing to me at that age.
I answered some of his questions and then he asked me if he could talk to me at length privately, and said he would pay whatever fee I might charge for a private show for an hour of my time. I asked for $100, thinking it was a ridiculously high amount of money, but he said fine.
I went to his apartment on Park Avenue, which was a duplex on top of a very fancy old building that had a private elevator. It was bigger than most houses. We sat in his library (all beautifully panelled in dark wood with his Oscar for Butch Cassidy on the shelf). I think that I found out who he was between the time he asked me to come to his place and when we eventually got together.
Either way, he asked some very specific questions, such as could I show him a trick that would be very difficult to get out of if someone shouted out the secret in the middle of the performance. I demonstrated the Phoenix Aces, and explained that if someone shouted out that there was more than one card you were a dead duck. You could, of course, palm off the extras, but if someone then demanded to see both hands empty you really couldn't get out of it. And this scenario ended up in the book, though he called the trick the Rising Aces.
I gave him a lot of the magic terminology that appears in the book, and suggested some books he might buy. I was not the only person he spoke to--he definitely talked to Dingle at some point, but I have no idea what they discussed.
I don't know where he found "Do As I Do," which he explained to great effect at a critical plot point.
I enjoyed the book when it came out, but it got terrible reviews. Goldman's career as a novelist had declined after Marathon Man, and aside from his non-fiction books about Hollywood, his novels were generally panned. He stopped writing novels altogether after the sequel to Marathon Man and has written many screenplays since.
The movie of MAGIC is awful, miscast and just plain bad. Of course, Goldman's "trick" novels (of which Magic was one) all have an inescapable problem when translated to the screen--you can SEE things that are hidden when you read, and so a gimmick like not knowing that Fats was a dummy, which goes on for quite a while in the book, can't be translated to the screen.