It exists in 3 versions : 2 days, 4 days and 6 days (consecutive calendar days)
You can buy it in advance (the valdidity starts when you enter the 1st museum)
It costs 30 ? for 2 days, 45 ? for 4 days, 60 ? for 6 days (to compare : one single museum ticket costs 8 or 9 ?)
Even, if you are a moderate museum fan, the pass has the interesting charateristic to allow you to skip the tickets lines (and, for some museums like the Louvre , to use separate entry gates) . This make a huge difference in high season when the queues are important.
Nota : the pass doesn't allow to skip the security check (the only place where it makes a difference is the Sainte Chapelle)
http://www.parismuseumpass.fr/flash/hp_fr.htmlMost parisian museums are freee under 18 years old, but if the parents have a pass, the acompanying children can use the same line (and skip the tickets line too).
The pass even allows you just to enter a museum to use the (generally very clean) toilets (even if you don't visit it)).
You can buy your pass in the museums (chose a small one with next to no queue to do this, like the Conciergerie or the Cluny) but also in the Paris tourist office (25 rue des Pyramides), in the shopping mall under the Louvre (Caroussel du Louvre) or in one of the FNAC shops (www.fnac.com).

