One of the highest compliments one can bestow on a piece of nonfiction is that it’s so compelling that it reads like fiction, that the characters and scenes are so vividly rendered that it’s hard to remember they actually happened.

To “Juliet,” the stunning new historical novel by debut novelist Anne Fortier, I heartily pay the same compliment — in reverse. This is fiction executed with utter believability, offering up people and situations so real you’d swear they’ll turn up on “Larry King Live” any minute now. I’m pretty certain that the next time I see a production of “Romeo and Juliet,” whose plot serves as a starting point for this book, I’ll be nodding sagely and thinking, “Oh, but I know the real story.” Right before I remember that this, too, is fiction.

Fortier tells the tale of modern-day 20-something Julie Jacobs, who, when an elderly aunt dies, discovers that her real name is Giulietta Tolomei, and that she’s a descendant of a noble Sienese family whose centuries-long rift with the neighboring Salimbenis may have been the real-life, 14th-century inspiration for “Romeo and Juliet.”

Julie was born in Italy, but moved along with her twin sister, Janice, to the United States when their parents died. Julie’s only excursion since to the motherland, when she was in her teens, involved protests and Roman police, so she’s not exactly welcome back. But when a mysterious letter from her mother comes to light — having been squirreled away by Aunt Rose for decades — Julie becomes Giulietta once more, with the help of a family retainer who apparently has excellent passport connections, and heads to Siena to search out her legacy.

Upon arrival in Italy, Julie is taken under the wing of a Salimbeni matriarch (which seems odd, given the families’ history) whose nephew, a bank security director, flirts both with Julie and with the idea of exposing her illegal presence in his country.

Things get complicated via the discovery of other artifacts and their relationship to historical legends (you know, the usual: a swatch of silk, diaries and more letters, a golden ring, a long-buried statue, Charlemagne) and a menacing black-clad figure on a motorcycle. With Giulietta’s diaries as her guide, Julie travels through centuries — not to mention the occasional Sienese sewer — in her quest.

At some point, she starts to wonder if that “plague on both your houses” curse is still in effect. “Was I insane?” she ponders. “Maybe. But then, there are many different kinds of insanity. Aunt Rose had always taken for granted that the whole world was in a constantly fluctuating state of madness, and that a neurosis was not an illness, but a fact of life, like pimples.”

If all this is starting to sound a bit “Da Vinci Code”-esque, it is, but in the best possible way. Fortier combines Dan Brown’s undeniable knack for plotting with the kind of elegant, witty writing that has made Philippa Gregory a superstar of historical fiction. Fortier perfectly juxtaposes the present day with the 1340s, creating a supersonic train of narrative that hurtles the reader along.

Fortier’s way with humor and romance nicely complement the darker plot elements, and 14th-century Giulietta is much feistier and, frankly, more fun, than her Shakespearean doppelganger. The centuries-apart Romeos are a tad less well-drawn, but convincingly dashing, heroic and amorous.

The author nicely, if unintentionally, sums up her own narrative wizardry with this passage near “Juliet’s” end: “The tale must be of Romeo and Giulietta, and it must contain much poetry and much confusion, as good art does, for an accomplished storyteller brimming with dazzling falsehoods commands far more attention than an honest bore.”

This storyteller dazzles, indeed, and “bore” will surely never be a word that’s applied to her work.