The Strange Case of Finley Jane
Publisher: Harlequin Teen
Source: Free NookBook!
You can read the Goodreads summary here.
So I wish I had known about this prequel before I read The Girl in the Steel Corset. Even having read it backwards, though, it turned out to be a really good piece of writing. It's free for Nook and Kindle and it would be a great way to learn more about Finley Jayne before you start TGITSC. I'd say if you were on the fence about reading TGITSC it would be a great way for you to discover more about the author's writing style, but trust me, you want to read TGITSC.