First thing to know is it is all in Italian without automatic sub-titles; so you will need to turn on the manual English sub-titles.
The acting is OK, with some possibly more well known Italian actors/actresses. What does shine through is the sheer sense of fun and enjoyment and oh boy, those cars are the real super stars.
Within the story of the Rosso Mille Miglia and how it works and showing off the cars, there is the underlying story related to the characters and in some ways the cars too - with some nice twists and suprises:
1) Where is the Superba
2) Did the grandfather really commit the incident he admitted too.
3) how involved was his partner.
4) Why didn't the partner ever race again.
5) Will the two co-stars get together.....
And loads of other questions which are slowly and superbly answered through the tale of he story...
By the end of the story everything is fully revealed and answered.
Would I buy it? No.
Would i watch it again? Possibly for the magnificient classic cars that are continuously praded through the movie.
Worth watching? Yes, especially while free on prime.