This play is definitely an interesting read, but I can't see how it would play out on the stage when the audience can't read the stage instructions (like letting you know that a guy in a straight-jacket is the TV, and other such low-rent "quirks" that this script has).
The Day Room definitely raises interesting questions about what is real and what is an illusion. The circular ending really saves the entire play, but it can't make up for 111 pages of confusion before that. While trying to build up to the shocking and consciousness-raising ending, the play sputters for a while in pseudo-intellectualism and leaves the reader wanting at least a little clarification to hang their hat on. Some randomness is beautiful, too much leaves nothing solid to hold the randomness up, and throws the reader off.
Delillo's style is reminiscient of Beckett and other experimental minimalists. There's not a typical plot, with a character arc to follow. There are hospital patients, and hospital workers, and the audience never really knows who's who or what's going to happen next. At times this is exciting, but at other times it separates the reader from the story.
There are some very good monologues sprinkled throughout the play, both in Act I and Act II, but sometimes long-winded monologues can get boring and slow a show down on stage. And if you're looking for good monologues, look somewhere besides a long-winded production set in a psychiatric ward.