Dan R. Deneyer
Google
We decided to visit the "museum" mainly because it was a cold, rainy January day and we wanted to stay inside for a while, therefore expectations were very low.
The museum itself is small and carved into what seems the insides of the old city. You get a listening device at the entrance and then watch a 3-D movie about the knights in a tiny theatre.
That can be informative if you know nothing about history.
Afterwards you can go into the narrow corridors and staircases where many "exhibits" show scenes from the history of the knights, some good, other less and in need of being refreshed.
For me it's a take-it-or-leave-it experience, peculiar but probably not so pleasant to visit in hot weather, when walking around in Mdina is more pleasant. Entrance fee 6,50€.