For people who have read my novel, or whoever

[ree-Xi]

I think that you might have an uphill battle here. According the US Copyright site:

"(b) In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work."

Think about movies that come out within weeks of each other, that share huge plot lines, similar story conflicts, protag/antagonists, settings, sequence, etc. For example, "Armageddon" came out two months AFTER "Deep Impact" (but was more successful). Other examples are "Antz" and "A Bug's Life," and "Dante's Peak" and "Volcano."

Most of the info I know deals with screenplays and protection advice from the Writer's Guild of America, but there might be some good information on their site. They suggest re-registering work when revisions are made; basically holding your ownership through additional revisions.

One question - do you retain a literary agent? Someone who works on your behalf? If not, you might be able to get some help from your publisher, even if it's just advice or suggestions on who else might be able to help you.

Good luck; we writers become married to their pieces of work, and it's scary to think that someone else is trying to capitalize on your ideas, efforts and successes. The situation does seem pretty sketchy to me. Definitely go to the play, and jot down phrases that might sound familiar to yours, any common themes, characters, places, events, even names. If not prohibited, bring an audio recorder and record some parts of the dialogue.

Like others, I'd love to read your book. Keep us posted on what happens!!