I have read works by classic playwrights (Tennessee Williams, Arthur Miller, Eugene O'Neill) as well as a work by a modern playwright. That modern playwright is David Mamet; the play is Glengarry Glen Ross.
Mamet has to be one of the more...explicit playwrights I have read. Explicit as in his characters speak their minds more than once and explicit as in his characters drop the f-bomb more than once.
Glengarry Glen Ross in some ways is a modern take of Death of a Salesman. The character in Glengarry Glen Ross that represents Death of a Salesman's Willy Loman best is Shelley Levene, who in the movie is played by Jack Lemmon in his best work. Like Loman, Levene was once a big shot who now struggles to scrape by. It's a complex role that only a great actor can play and Lemmon nails it.
Along with Lemmon, the cast for Glengarry Glen Ross includes Al Pacino, Kevin Spacey, Ed Harris, Alan Arkin and Alec Baldwin, the latter has the most epic scene (Mamet wrote it for the movie). It's an ideally chosen and well-acted cast. Could there be a more perfect one?
What's worth checking out?: I'd go with both.