Yesterday, after the initial crisis concerning Witherwilds, I did more research on the offending, already-published novel and found that aside from some trappings, I'm telling a very different story from the other. However, the fact remains that I have to eradicate or at least twist and disguise the similarities. I've decided that discovering the existence of the other book was a blessing. How horrid I would feel if I'd never heard of it, finished my work, and then discovered it after the details were more firmly realized in my mind, or after trying to get it published. The cloud definitely has a silver lining.
At this stage, changing the superficial elements is relatively easy. Relatively. Also, it just pushes me to accept what I already knew: a certain aspect of my book was not quite fresh enough.
I still believe that the key concept and the (hopefully) frankness with which I hope to approach it is fresh enough in a fantasy setting. I have to plumb that concept to find a MacGuffin that will lend resonance to the story as a whole.