In her new memoir, The Secrets of My Life, Caitlyn Jenner gets candid - very, very candid - about all aspects of her life, past and present.

By tell-all standards, this is a doozy. She is telling ALL.

Among the topics at hand? Her two-decade marriage to Kris Jenner, with no holds barred regarding the many ups, downs and confusion therein.

Caitlyn has already dropped a couple of mini-bombshells.

Asserting that Robert Kardashian knew O.J. was guilty and that Kris knew Caitlyn was trans from day one, Jenner is trying to sell books.

If those and the latest excerpts - which discuss her sex life with Kris - reflect the memoir at large, it may well be a global bestseller.

“We fall in love quickly (we marry after seven months),” the Olympian, 67, writes in an excerpt published today, cutting right to the chase.

“Since - let’s not kid ourselves - everyone wants to know, Kris and I [had] good and frequent sex at the beginning.”

The former Bruce Jenner, who transitioned into a woman and took the name Caitlyn two years ago, says it was still awkward, though.

Caitlyn describes the sex as “imbued with love” but admits she wasn’t “entirely comfortable” with the act of making love to Kris Jenner.

“I tell Kris about my gender issues before I make love to her. This will always be a subject of dispute between us,” she laments.

“She insists that she was taken by surprise by my ultimate transition to Caitlyn, which obviously means in her mind that she did not know enough.”

In January, Caitlyn underwent gender reassignment surgery to make that transition physically complete. But it was a long time coming.

Jenner says that on a number of occasions during their relationship, she dressed as a woman in front of Kris ... and had 36B-cup breasts.

In 1990. When they met.

Cait attributes her chest then to hormone therapy, while admitting that she often stole makeup and clothing from her wife and daughters.

“I have bought makeup how-to books,” Caitlyn adds.

“I keep the [makeup] books, along with my meager collection of clothing, in a small closet with a lock in the back of my closet." 

"Kris and I have negotiated this," she recalls of that time period, "since she is terrified, as I am, of the kids finding something.”

Strange as it was to have sex with Kris while she felt like a woman herself, Cait says the public interest in her sex life now is stranger still.

“I don’t have the appetite for [sex], which is why the public’s obsession over [my gender confirmation surgery] is annoying," she writes.

“It hearkens back to this misperception that people transition because of their sexual desires," says the transgender advocate.

Which isn't to say he doesn't have any.

The thrice-divorced Jenner admits that she has in fact thought about what it would be like to be physically intimate with a man.

On the flip side, she's still into women ... in a sense. In a section completed before she had the surgery, Jenner muses on the subject:

“A future female companion? I think about that. A future female sexual companion? Not happening, at least for now, and perhaps not ever.” 

“A future male sexual companion? I have never had the inclination. But maybe that attitude might possibly change if I have the Final Surgery.”

All in all, Caitlyn is focused on living life and spending time with family, including daughters Kendall, 21, and Kylie, 19, from her marriage to Kris.

She also shares Burt, 38, and Cassandra, 36, with ex-wife Chrystie Crownover, and Brandon, 35, and Brody, 33, with Linda Thompson. 

While his former wives have a lot of mixed feelings for obvious reasons, the kids - and his stepchildren - have been overwhelmingly supportive.