But going back 10 years, to say that Horovitz found the atmosphere intimidating in his first weeks would be an understatement. "I was American, I was a student and I was a trainee caddie so pretty quickly I realised that I was the scum of the world. They hated me. They were like, you've been here 10 seconds, who the hell are you?
"I was being screamed at on a daily basis for making all the caddie mistakes I didn't even know existed. You're not meant to correct the older caddies, you're not meant to be loud, you're not meant to hold forth over the rest of the group. I was doing all of those things."
But, slowly, his hard work and determination to learn every nook and cranny of the course won over his colleagues - and a very scary caddie master called Rick. And Horovitz came to appreciate that there might just be a coming-of-age story to be told. "The funny thing is that everyone has these life experiences - your first success with girls, the first time you stood up to a bully, the boss who scared the hell out of you. Yet for me all these dramas were played out at St Andrews."
His relationship with his English uncle Ken - a town councillor who lived in St Andrews for years - also plays a big part in the book. Indeed, it is fair to say that Horovitz has an interesting family history. His father, Israel, is an acclaimed playwright. His mother, Gillian, was a British-born marathon runner who competed for England in the 1998 Commonwealth Games, finishing fourth. And his half-brother is Adam "Ad-Rock" Horovitz of the Beastie Boys.
But he did not feel pressure to succeed. On the contrary, the family philosophy seemed to be to go off and try new things. "You can go and do what you want. I come from a very hard working family who have done some cool stuff."
He soon became known as the golfer in the family, an interest he inherited not from his athletic mother but from his literary father. "My father caddied in a very Waspish area when he was growing up. It was a big course where no Jews were allowed. Yet all the caddies were Jewish and were given Christian saint names. So instead of Bernie or Israel, you became Edward or Paul."
Being Jewish has never been a problem for him at St Andrews. There is a caddie from Zimbabwe who has spent time on a kibbutz who wishes him Shabbat Shalom every Friday and he once received a text from another caddie while out on the course asking him if he knew "what mossletov means in Jewish".
Horovitz followed in his father's footsteps and started caddying on his local course to make some money. He also became a good enough player to be recruited to play on the Harvard team but his year at St Andrews made him realise that he was not going to be a professional. "I played on the St Andrews team. There was no professional supervision, just 25 players who were all pretty much good enough to turn pro. The standard was incredible - they would destroy any American golf team so for me it was a test. At the end of it, I had had an amazing time but I knew I was not going to make it as a pro."
However, being out on the course as a caddie is an excellent consolation prize. "In the shack, what I found out was that most of the guys had dreamed of being pro golfers but this was the next best thing. They are living the life of their dreams, they are caddyng in big tournaments and they have made golf their life. That is so cool."
During the course of his career, Horovitz has carried bags for some big names, including his hero, Larry David, plus Michael Douglas, Andy Garcia, Ian Botham, Rory McIlroy and singer Huey Lewis, for whom he now caddies every year in the pro-am Dunhill Cup.
Having gained so much experience, he knows instinctively what kind of round he is in for. Caddying for a good golfer means there will be considerably less walking and hunting for balls, but essentially he likes a golfer who wants to enjoy the experience. "If you're a nice guy and excited to be at St Andrews, that's all we want. It doesn't really matter how you play. The coolest thing about the job is that the men and women we caddie for are basically having the best four hours of their lives. These are people who have dreamed about getting to St Andrews. I have had 70-year-old men break down and start crying on the second hole."
But the sight of a huge bag makes him groan. "There's a saying in the shack, the bigger the gear no idea. I've never met anyone I liked who had head covers on their irons."
Horovitz also works as a film production assistant in the US. But he intends to continue spending his summers carrying bags for £45-a-round plus tips. "You might be a world leader or the president of IBM but for four hours out there on the Old Course, the caddie is in charge."
