Feint of Art by Hailey Lind (2006, Paperback)

Ms. Lind also writes under the name Juliet Blackwell for her paranormal series which is also quite good!
In "Feint of Art", the heroine is Annie Kincaid, who was a prodigy forger by the age of ten years, under the tutelage of her grandfather, Georges LeFleur, THE master forger. That was cute when she was younger, but as she aged the authorities didn't see it quite that way, and so Annie is now trying to make an honest living as a faux finisher in the San Francisco area. The story begins when she receives a strange call from her ex-boyfriend, Ernst Pettigrew, who is now the museum curator for the snooty Brock Museum. Meeting him at midnight and being ushered into the Brock's vault, she discovers that what should be the priceless 15 million dollar painting, The Magi, painted in 1597 by Michelangelo Merisi de Caravaggio, is definitely a fake, and she knows of only two forgers who could have mastered this type of work. Her grandfather or his good friend & rival, Anton Woznikowicz. The night isn't over for Annie as she learns that after she left the museum, Ernst goes missing and the guard that secretly let her in and out is shot to death. No stranger to the network of art dealers and artist, she finds that a well-known art dealer has absconded with multiple Old Master drawings, leaving forgeries in their place along with a lot of angry people. In the meantime, The Brock still thinks it has the original masterpiece, but that all changes when an encounter with a very charming, handsome art thief draws her into his underworld where someone is killing off people to get to the original painting. Another enigma is the new owner of the building where her office wherehouse resides. J. Frank DeBenton, dressed in Armani and no smile, seems to deem Annie undesirable as a tenant, until some mobsters kidnap her and he is the one to come to her rescue without so much as wrinkling his suit.
Lots of crazy and colorful characters in Ms. Lind's book that make for late night reading. You'll also learn something about art and art forgery along the way. The side trips out to Napa and other places are colorfully written as well as her descriptions of the Bay area and Oakland. This is the same setting in her paranormal series. Good reading!