I couldn't find the recent thread where many of us chewed over whether or not the Louvre and the Mona Lisa are worth the trouble (this topic has come up many times in the forum over the years) so I'm adding this note here in recommended reading --
James Gardner put out a great new overview of the history of the Louvre that really brings it alive this past summer, under the title
The Louvre: The Many Lives of the World's Most Famous Museum (Atlantic Monthly Press)
and he does a great job of connecting the museum to all of modern western history and art and architecture.
You can see a typically erudite review by Adam Gopnik in The New Yorker issue dated 26 October [print issue]
The online version is dated a week earlier.
Gopnik points out that most of the best items in the museum were all added by 1870 and were there for the Impressionists and Modernists to learn from, but the scope of this book doesn't go very much into how art production and collection continued and still continues today, available in the tourist-favored Orsay, etc.