Yaroslav K.
Google
Ok, this is not a museum but a very very nice showroom. Free and great experience. If you are in Modena it’s recommended to visit. It’s not far away from Enzo Ferrari museum so you can just walk.
If you really into Maserati, I’d recommend to visit Paninj museum that has a big collection of Maserati cars, one of the biggest private collections AFAIK and it just 15mjn away by car. BY the way Paninj museum is also for free, but accepts donations.
Btw, did you know that Maserati logo comes from the Neptune fountain in Bologna?)