Fans of Mark Haddon’s novel “The Curious Incident of the Dog in the Night-Time” will cherish the National Theatre production that has finally found its way to Broadway—but they may be in for a surprise, too. On stage, they’re getting a bolder, braver and happier Christopher Boone than the one evoked by the 2003 best-seller.

With Broadway newcomer and recent Juilliard grad Alex Sharp bringing the boy to life in the new production that has just opened at the Barrymore Theatre, Christopher is still “ill-equipped” to interpret everyday life, but he’s also far more assertive than the nervous teen of the novel, not to mention more capable of both holding a grudge and experiencing joy.

Director Marianne Elliott (“War Horse”) begins audaciously, depicting center-stage the bloody body of a dog, Wellington, with a “garden-fork” protruding from his side. The reveal transpires amid nearly seizure-spurring spasms of light, until we finally see Christopher frozen in place, confronted by Wellington’s owner, Mrs. Shears (Mercedes Herrero), demanding to know: “Holy f—-. What have you done?”

After Christopher falls under suspicion of killing Wellington, he embarks on a quest to learn the killer’s identity, but in doing so, uncovers a jarring family secret. The first act, largely narrated by his mentor, Siobhan (played gracefully by Francesca Fardinay of “The 39 Steps”), sets up the circumstances of the boy’s current living situation. The second is about the physical journey Christopher takes to get to the bottom of matters.

Ian Barford is solid as Ed, Christopher’s father and primary caretaker, a working-class Brit who could have walked out of “Billy Elliott,” except here, his problem isn’t Margaret Thatcher … it’s controlling himself enough to care for his son. Enid Graham gives a layered performance as Judy, Christopher’s mom, barely an adult herself, and a woman perhaps incapable of managing a child with her son’s needs.

We meet Judy in a memory Christopher recalls from a family vacation. She’s dressed provocatively and smoking a cigarette, encouraging her son to join her in the ocean: “There aren’t any sharks in Cornwall,” she’s pleading. I found it easy to understand the bond between this mother and child, even as I sympathized with Judy’s other, more selfish motivations.

It’s not spoiling anything to reveal that infidelities are at play with both mom and dad, and it was fun to walk out of the show and argue about which one of the two was the better parent. They’re both clearly drawn and ordinarily flawed human beings.

The greatest accomplishment in this superbly directed production (it’s been adapted for the stage by Haddon’s friend, playwright Simon Stephens) is its uncanny ability to make us experience Christopher’s emotional challenges, whatever you prefer to call them, from the inside out, both audibly and visually.

So, when Christopher descends into London’s Underground at the beginning of the second act, we experience, via clever use of the small ensemble and a lot of technical wizardry, how it must feel to be a boy who can explain the Pythagorean theorem, and be awfully cocky doing so—be sure to stick around for a brief coda after curtain—but who also becomes paralyzed if he’s around “yellow things or brown things.”

We don’t fully realize how important Sibohan’s role is in Christopher’s life until we hear her in voiceover, helping Christopher gain control over his mind when he’s in the crowded Tube.

The production design is electric, intricate, icy and certainly unprecedented—woe the Con Ed bill at the Barrymore. Rather than a customary set, the drama unfolds inside a digitized coordinate plane, a suitable environment for the “maths”-obsessed Christopher.

In the most dramatic moments, Christopher scales the set’s back wall, and then descends as it transforms into an escalator at London’s Paddington Station. Moments later, we’re leaning forward in our seats as the boy, unfamiliar with dangers of the Tube, chases his pet rat, Toby, onto what has quite frighteningly become a subway platform. It’s whiz-bang theater stuff that’s simply a thrill to behold.

We’d talk about Christopher today as falling “somewhere on the autism spectrum,” though Haddon would prefer we thought of him simply as “an outsider,” a stance that makes the story that much more of a relatable experience. This kid up on stage, as portrayed by the nimble Sharp? Well, he’s me. And my friends. And probably you, too, on any day when you feel overwhelmed, or more than a little obsessive-compulsive.

“The Curious Incident of the Dog in the Night-Time,” with an open-ended run at the Ethel Barrymore Theatre, 243 W. 47th St. Tickets: $27-$129. Call Telecharge, 212-239-6200.

--Follow Robert Kahn on Twitter @RobertKahn.