This book would have some potential if it weren’t full of entries like “In 1954, a man ejaculated 15 ml.” That’s all it says on the topic, no name, no source.
I’m sure the contents of this book were scraped together from a few websites and condensed into a crummy Kindle book in a couple of days, but I’d like to imagine that the author compiled it from his own research, hours and hours of knocking on doors, asking people “So, ever have a really large nude wedding? No? Okay, how about a… (looks at paper) anal gangbang with over 40 participants? No? Okay, thanks for your time.”
(If you’re in the mood for more unverifiable “sex world records”, there is, as always, the “look inside” link.)