There is so much incorrect information in this thread that there is no one good place to start.
It ranges from "just ignore copyright" to "the sky is falling if this picture goes in the book" and both are wrong.
A a professional involved with publishing and also restoration of copyrighted works, I have been involved with these issues for a long time.
People need to step back and take a deep breath or two.
First, is the art copyrighted? Of course it is. Read this:
http://www.copyright.gov/title17/92appvi.html
Second, is it legal to take pictures exploiting the artists work for profit? Of course not.
However, ->IN THE USA<- (I have NO IDEA about countries that are not signatories of the 1989 Berne Convention for the Protection of Literary and Artistic Works) you CAN take and publish pictures with copyrighted works of art in them provided the photograph meets certain 'tests', the primary one being is the copyrighted object itself the subject of the photograph and is the possibly infringing work profiting from the display and sale of the image of that art.
In the sample photo above, neither of these apply.
It is especially noteworthy that all copyright law awards turn on the infringer reaping monetary rewards at the expense of the copyright holder. Someone downloading music on the Internet, for just one example, steals income from the copyright holder and therefore reaps a monetary reward from the theft (they didn't pay for the music). The lawyer I retained to establish policies for my restoration business basically said "No monetary damages, no foul" was the general rule.
Here is some light reading for those so inclined:
http://www.copyright.gov/title17/
Please note it is US LAW ONLY and other countries laws will certainly vary.
Also, for your further edification, just stop and logically think of the consequences if the law were interpreted any other way.
~ You would never be able to publish a photograph that had a billboard in it because you would be violating the original photographers copyright.
~ You would never be able to publish a photograph with an automobile in it because those designs are copyrighted.
~ You would never be able to publish a photograph a bus on a city street with advertisements on the side as you would violate both the copyright holder of the bus and the copyright holder of the ad.
etc., etc., ad infinitum
The photo above is of people. A peripheral part is the inclusion of the work of art. It is not the subject, not is the photograph intended to profit from the inclusion of the art.
No foul.
Tom