I found "Battle Dress" by Amy Efaw to be the most realistic portrayal of Beast that I've read, albeit from a bit of a female perspective. She was in the class after mine, and everything I read was just exactly what I experienced. Now that was 25 years ago, but I've heard from people even at the academy now saying that it gives you a good representation, and is an easy, fun read.
Another book by a cadet I knew at WP, "A Matter of Trust", by Mark Vakkur, is more a story of what can happen when there is too much stress, when it's someone with too much power. This one is a bit far-fetched, but many of the portrayals of cadet life are accurate, and I think anyone who had attended there would have known at least one cadet that they could see resulting in this story!
And of course a classic is "Dress Grey" by Lucian Truscott. This takes place during Vietnam, and is a much more serious book, but it also gives some good background to the history of life at the academy over the past decades.
Finally, I just read "In the Men's House" by Carol Barkalow. This is basically the story of the first female class at West Point, but again it gives you insights into how women played into the history of the academy, as well as glimpses into academy life.
I'd consider the first book much more of a must read in preparation. I know I read everything out there before I went, and was always looking for more. Even if your son doesn't want to read them, you might enjoy them all even after he's gone (to keep in the same mindset).
One book I'd have to recommend against was called "Understanding West Point: What Cadets must do at West Point and Why" by Norman Remick. I thought it would be very informative, and it had good reviews, so I bought it for my husband recently. We both just couldn't get through it since it focuses much more on historical events during Jefferson's time, rather than anything recent. I guess if you're a big history buff it might be interesting, but it certainly wasn't practical. Just didn't want you to go buy it on Amazon like I did expecting something entirely different!
The other more recent option would just be to do youtube searches for Beast, R-day, cadet life, spirit missions, things like that. You could literally spend a whole weekend watching all the videos that are out there. That's what we did to find out about SLS this summer. My son wasn't sure he would fit it in (he's also doing Navy and AF's summer seminars), but after watching all the clips, he decided he really wanted to go there and experience all the cool things they did.
Good luck!