There are 5,797 reviews of the London show on TripAdvisor, which should give you plenty of reading to do!
Here's a breakdown of those reviews:
Excellent 81%
Very good 10%
Average 3%
Poor 2%
Terrible 4%
https://www.tripadvisor.co.uk/Attraction_Review-g186338-d3905591-Reviews-The_Book_of_Mormon_London-London_England.html
With 91% of reviewers rating the show as either 'excellent' or 'very good', it would seem that there's a good chance that you'd enjoy it but, with 6% finding it either 'poor' or terrible, I suppose that you might not.
I've not bothered to find the poorer reviews but I do note that things like "not for those easily offended" do seem to occur quite often in some of the other ones. Perhaps it's people who've been easily offended who've posted the poorer reviews?