A good way to begin a tour of Le Marais, and the old Jewish quarter. This is very similar to Jewish cultural museums in other major ciites; ritual objects, ketubot, tallit, etc., but it is remarkably well-organized and easy to naviagate. Your entry fee gets you an audio tour in English or French, which enables you to move back and forth between entries and exhibits. There are a lot of historical documents on Jewish life in Spain, England, Italy, Germany and the Netherlands as well as just France, and some heart-breaking accounts of pogroms and expulsions. Good section on the WW II experience too.

Allow plenty of time: I expected to breeze through it and found myself staying over 2 hours. While it seems designed for those with little or no knowlege of Judaism, (lots of explanations of the holidays and lifecycle rituals for example) there's plenty to interest Jewish visitors as well.

One caveat: this is NOT part of the Paris Museum pass package, so you'll need to pay a 6 euro entry fee. Well worth it though.