In her portrait, she is young, with cherry blossom skin, glimmery long hair and eyes the color of Anjou pears. When Peter Silverman first saw the drawing (in chalk, pen and ink on vellum), he was entranced by the sitter’s beauty. But something seemed off. The Christie’s auction house catalogue described the 9 inch-by-13-inch work as that of a German artist from the early 19th century. Impossible, Silverman thought. Owing to its exquisite detail, the portrait appeared to be the work of a genuine master, perhaps even the master of them all, Leonard da Vinci.

In his new book, “Leonardo’s Lost Princess,” written with Catherine Whitney, Silverman recounts his journey to vindicate his hunch. A serious art collector with serious funds, Silverman bought the drawing in the winter of 2007 at a private gallery in New York for $19,000. Many art critics scoffed at his notion of who had made the portrait, which came to be known as “La Bella Principessa.” But Silverman persevered, consulting with many of the art world’s top Leonardo experts. He found through carbon-14 dating that the vellum dated not from the early 19th century, as Christie’s had reported, but from between 1440 and 1650. He found more evidence supporting Leondardo as the artist by using high-tech cameras to take images that peeled the painting away layer-by-layer.

To the chagrin of the naysayers, Silverman was able to prove his point beyond a doubt. The drawing’s appraised value is now $150 million. “I had achieved the dream of every collector: to bring to the world a previously undiscovered Master work,” he writes. He also uncovered the history of the portrait and learned the identity of its subject. She was Bianca, the illegitimate daughter of a Milanese duke, and was to be married to the duke’s army commander. Da Vinci created the portrait in honor of the marriage.

Silverman’s book is a fascinating tale with Da Vinci Codesque twists. But one mystery is never quite solved: Who is Peter Silverman? The little we learn about him is that he was a Brooklyn immigrant kid who made it big and now lives in Paris. Readers may finish his book wanting to learn more about the motivations of a man who puts so much effort, and lots and lots of money, into what is in the end a very expensive hobby.

—T. Rees Shapiro

shapirot@washpost.com