I'm not the person to wholly enjoy plays, however, both of Shaffer's plays take the cake for well written plays. 
Amadeus is, well Amadeus. The play is well written to highlight both Salieri and WAM's life. Both serious and comedic, this play will impress many people. Read this before the movie, and I HIGHLY recommend the movie. There's always a slim chance that the movie meets the expectations of the book based off of, and this is one of those examples.

Who do I recommend it to? Music lovers, people who love drama, people who enjoy historical fiction, those who want to read a good play.