Founder of #GIRLSLIKEUS Janet Mock speaks on stage at the ADCOLOR Awards at The Beverly Hilton Hotel on September 21, 2013 in Beverly Hills, California. (Mike Windle/Getty Images for AdColor)

“Stephen! I’m moving in,” Janet Mock says to her host, walking toward the second-floor study on a catwalk of plush oriental carpet. “And I have good news. It hit No. 19.”

Stephen Bennett whoops his congratulations as he heads downstairs, where the doorbell is already dinging and donging. Mock settles onto a white chair in the study, a giant painting of the Galleria Borghese to her left, a dark fireplace to her right, guests beginning to arrive below.

“It” is her book.

“No. 19” is its position on the New York Times bestseller list for hardcover nonfiction.

She had three goals when she was growing up as Charles Mock in Hono­lulu.

"Redefining Realness," by Janet Mock (Aaron Tredwell for Atria Books)

“I wanted to be myself, I wanted to be a writer and I wanted to live in New York City,” Mock says. “And I’ve accomplished those things. So now I have to dare to myself to dream bigger. And that’s kind of where I’m at right now.”

Right now, on this snowy Wednesday evening, she is on the third floor of the Dupont Circle rowhouse of Bennett, president of United Cerebral Palsy and Mock’s fellow board member on the Arcus Foundation, whose social justice portfolio includes LGBT equality. Janet Mock, 30, is the current It Girl for the “T,” for trans issues, for her book “Redefining Realness: My Path to Womanhood, Identity, Love & So Much More,” and for last week’s two-part appearance on “Piers Morgan Live.”

The first segment was smooth and cordial, though the onscreen text under her name — “was a boy until 18,” which is contrary to Mock’s identity — was a ticking time bomb that later exploded on Twitter.

The second segment, set up to respond to the controversy over the first appearance, was a bit tortured, as the CNN host confronted Mock for not confronting him on the air about his misunderstandings of trans culture and terminology.

“I was in a space of trying to educate and be a kind person toward someone who’s well-meaning but ignorant,” Mock says of the first appearance. “The next day when I went on, it was different. I wasn’t in that space any more. I was angry. I expressed my anger and my pain. And I think — I think I left the social-justice bubble.”

She emits a long sigh that dwindles to a grumble.

“I think that’s what I really learned this week — that there’s a hunger to know more about this trans stuff,” Mock says, “and [people] feel as if they haven’t really been given the words, the language and the stories to discuss it.”

The wider world has always been way behind on trans issues, from the moment in 1952 when Christine Jorgensen deplaned on American soil after undergoing the first-ever successful sex-change operation, to last year’s hand-wringing by the media over how to refer to Chelsea Manning, who was first known to the public as Bradley Manning. Less than 24 hours after Mock’s book party in Washington, Facebook would allow customized gender identification beyond “male” and “female” (“Yaaas” would be Mock’s enthusiastic reaction on Twitter, followed by the hashtags #trans and #nonbinary). As she writes in Chapter 8 of her book, nearly 700,000 Americans identify as transgender, according to the UCLA School of Law’s Williams Institute, and most have taken medical steps to transition. Mock had her surgery at 18, and the book is a raw personal history that leads up to that event as well as a public example of trans living that she never had as a child and adolescent.

“I think about Ellen DeGeneres, seeing her every single day on a show,” Mock says as the muffled sounds of a baby grand piano reach the upstairs. “Her identity is there every day, but what leads the way is her talent and how much you like her. I want to create the content I didn’t have while growing up.”

More TV, she thinks. A series. Maybe a second volume of autobiography some day, once she’s put some distance between herself and this latest, craziest phase of her life.

Her book-party dress is half-white and half-black. Her heels are shiny and pointed and black. Her teeth are shiny and perfect and white. Her hair is a black-bronze frizz. She knows she could go “stealth,” and fly under the radar in a society attuned to any deviation from the norm. But she has chosen to be a public champion — with all the attendant scrutiny and frustration — for trans women who can’t leave their homes as themselves for fear of violence, who are fighting battles over such fundamentals as bathrooms and education and employment and poverty.

“For me,” Mock says, “the number one thing is to liberate the girls.”

The guest list has around 70 names and the hubbub downstairs is growing. Guests swipe mini-cupcakes from the sideboard in the dining room and chat in squished clumps by a burst of lilies near the front hall. The pianist, coincidentally, is playing “Don’t Cry for Me Argentina” as Mock descends the staircase to a smattering of applause. She falls into an echo chamber of “Hi how are youuus” and “You look beauuutifuls.” With a flute of champagne in hand, she turns from one hug into another. People lament the weather-related cancellation of Thursday night’s conversation and book-signing at the MLK library downtown. Nearly 400 people had RSVP’d to attend.

Standing by the house’s street-facing bay window, watching the warm reception ebb and flow, is Ruby Corado, executive director of LGBT community center Casa Ruby near Howard University.

“Our stories in D.C. have mostly been told through violence and disparity,” says Corado. “So to see someone young telling her story, and for me to be able to say, ‘She’s a role model’ — I’m very grateful.”

At 7 p.m. Stephen Bennett summons his guests to the staircase and introduces Mock, who alights on the landing and reads a passage from Chapter 14.

“I was a mixed black girl existing in a Westernized Hawaiian culture where petite Asian women were the ideal, in a white culture where black women were furthest from the standard of beauty, in an American culture where trans women of color were invisible,” she says, now the center of attention.