Despite the best of author intentions, which includes a great deal of research, this book fails miserably! The description of the code is far too confusing to follow, the way in which the main characters link up is washed away in a sea of confusion, the mysterious bit players who pop in and out of the story would have been better off out than in, and the plot-line makes no sense either.
Art restorer Natanya forges a Vermeer, which she and her boyfriend Philippe manage to exchange for the original, which they then trade for a volume of photographs of paintings believed to have been destroyed by the Nazis. (Up to this point the plot actually works. But no further...)
Then, together with the former director of the National Galleries and two NASA staff members (how this disparate group got together is sidestepped in one of the author's most annoying wash-overs) they go on a treasure hunt. Half the group works as code-breakers using sophisticated NASA equipment that just happens to be at their disposal, while the other half chases after the paintings in a borrowed helicopter (sure!) on receiving the code. Interestingly enough, on finding the buildings, or ruins of buildings, noted in the code it takes just a few hours to actually locate the priceless paintings (undamaged of course, despite a half-century of neglect) and load them onto the helicopters (at times there is more than one chopper).
The noble intent is to return the paintings to their former owners or their heirs. Had the author bitten off a smaller piece of plot (say, a hunt for one or two of the paintings), carefully fleshed out all connections among players, and treated the hunt seriously the book might have been a good, possibly a great one. This way, it is barely readable.