Mamma Mia! was the show that proved a musical could be assembled from an existing pop catalogue and still work as a story. The plot is straightforward: a young woman about to get married on a Greek island invites three men who might be her father, without telling her mother. The songs are ABBA's, arranged for the stage, and the book is written to carry them rather than the other way round.
That structure sets expectations correctly. Nobody comes for narrative complexity, and the show knows it. What it does well is momentum, a cast of adult characters who get real material rather than being scenery for the leads, and a final sequence that abandons the story entirely and turns the theatre into a concert. Audiences stand up. That is designed, not accidental, and it is worth knowing if you were planning to sit quietly at the end.
Because it has run for decades in multiple countries, the version you see depends heavily on the listing. Long-running sit-down productions in major cities have the full original staging. Touring productions play houses of very different sizes and adapt accordingly. Some international productions perform in translation. The venue and city on the listing tell you which you are getting.
For seats, this is a show where energy matters more than detail. You lose little from sitting further back than you would at a play, and the sound design in most houses is built for a big room. What you do want is a reasonably central position, because the choreography in the large numbers uses the full width of the stage and side seats cut into it.
Runtime is around two hours and twenty minutes with an interval. PickStub is an independent marketplace and is not affiliated with the producers of Mamma Mia!, with ABBA, or with the theatres staging the show.