These TV series are about sleepers - works of art by famous artists that escaped catalogs and were missed by auction experts. It is quite entertaining, and would appeal to people interested in old masters, impressionists and early 20 century art. The team spends amazing amounts of time traveling around the world in search for clues in archives, trying to cover gaps in picture's provenance, meeting world experts and performing pigment and canvas analysis. This process is like an exciting detective story, quite often more interesting than the picture itself which in many cases is a relatively mediocre piece by a famous artist (like in episodes about Monet or Degas). I think the most interesting episodes were about Van Dyck and Van Meegeren.
I hope they make the 4th season of this show. Since in most cases the paintings turn out to be genuine, it might be more interesting if more fakes would be shown, to make it less predictable. Also although the price aspect is important for owners and art dealers it would be great if the art and history aspect would somehow be given higher priority.