"The Art Forger" by B. A. Shapiro

This novel started out like Dara Horn's novel "The World to Come", with a report in the a newspaper about an art heist, in this case, a theft in 1990 of several paintings from the Isabella Stewart Gardner Museum including "After the Bath" by Degas. Years later, that painting (or is it a copy?) arrives in the studio of a talented (but tarnished) young lady artist in Boston who is bribed and cajoled into copying this stolen masterpiece. The idea is, according to the reputable (or is he?) art dealer, that a wealthy but unsophisticated foreign collector will end up with the copy and the Museum will get the original canvas, and everybody will get paid. The heroine, Claire Roth, makes a modest living producing perfectly legal copies of paintings for a specialty firm; now she turns her talent to copying a genuine masterpiece (which is kept in her studio/living space) for far greater gain and the hope the original will be returned to the museum. The art dealer naturally becomes her lover; she agonizes over  the ethics of her actions, but she is rather desperate for a hefty paycheck. The plot was not that strong; in reminded me of "Bridget Jones Copies a Stolen Masterpiece in Boston"--in other words, "Chick Lit".
However, I googled the Isabella Stewart Gardner Museum and the collector herself. The book tells some interesting details about the techniques involved in making a new canvas "look old", even to experts.