Dear Miss Snark-
I snagged an agent last year for my first novel. He's sent it to 11 editors and received 10 rejects and does not plan to send to any more (our 6-month contract is almost up).
Can I try to get another agent? I had another one very interested before I went with the one I have, one who sells more literary fiction. Will the fact that my agent wasn't able to sell it dissuade another agent from considering me? Should I send a list of the editors who passed to a prospective new agent? I've also revised the book recently.
No (but if by some miracle an agent bites, you'll need to be able to send it then).
This is going to be a VERY hard sell to an agent. Unless your agent called it a romance when it was a Western, it's going to be really hard to find someone to take this on.
You'd do well to query another novel and leave this one for the second book on a two book deal.