"Guttural sobs, the sort that make you heave for air, the sort that scares you," Sharapova writes of Williams' cries in the book, according to excerpts released by the New York Times this week.
"It went on and on. I got out as quickly as I could, but she knew I was there.
"People often wonder why I have had so much trouble beating Serena; she's owned me in the past 10 years. My record against her is 2-19.
"In analysing this, people talk about Serena's strength, her serve and confidence, how her particular game matches up to my particular game, and, sure there is truth to all of that; but, to me, the real answer was there, in this locker room, where I was changing and she was bawling.
"I think Serena hated me for being the skinny kid who beat her, against all odds, at Wimbledon."
Sharapova, who appeared on the verge of returning to elite form at this year's US Open after serving a 15-month doping ban, freely shares her opinions of Williams in her first memoir, a curious decision considering the two are still actively competing on tour.
Perhaps in Sharapova's mind, getting her feelings on paper will help her break through the mental barrier that has allowed Williams to walk all over her in the past decade.
The 35-year-old Williams has won their last 18 meetings.
"You are a speed bump. You are a zero. Many great players have this mentality. Serena Williams just has it more," Sharapova writes.
Sharapova admits she looked at Serena and her sister Venus in awe when she first emerged on the scene as a skinny teenager.
Still, she writes one thought rang loud and clear when she encountered the younger Serena back in the early 2000s: "I am going to get you."
Sharapova, now 30 and a five-time grand slam champion, has earned plenty of enemies after she tested positive for meldonium at the 2016 Australian Open (where she also picked up her most recent loss to Williams in the quarterfinal).
Eugenie Bouchard has called her a "cheater" and Caroline Wozniacki complained that she was getting preferential treatment Flushing Meadows.
But it seems the person Sharapova is most intent on becoming friends with is the one she can't beat.
"Serena and I should be friends: we love the same thing, we have the same passion," Sharapova writes.
"Only a few people in the world know what we know - what it feels like in the dead centre of this storm, the fear and anger that drives you, how it is to win and how it is to lose. But we are not friends - not at all.
"I think, to some extent, we have driven each other.
"Maybe that's better than being friends. Maybe that's what it takes to fire up the proper fury.
"Only when you have that intense antagonism can you find the strength to finish her off. But who knows?
"Someday, when all this is in our past, maybe we'll become friends. Or not. You never can tell."
