I go to B&N to write most of my first drafts. Part of my routine is to find a book or magazine to browse while I eat a cookie and drink a white mocha. Then I usually start writing. The other day I went and didn't find anything to read before grabbing a table. I like the window tables because I can gaze dreamily outside and ponder my next sentence or paragraph. And I like the window sill for my purse, so I found a window table and on the window sill was a book. It wasn't a book I would have picked up myself, but since it was just sitting there, I read the back cover. Then I opened it up and read the first chapter, and the next until I was up to page 128 and hadn't done any writing.
I love the unexpected. I love finding something I didn't know was coming. Especially when I'm writing. I love it when the characters surprise you by being especially witty or clever or devious. Sometimes so devious that you didn't even know they had it in them. My first and only adult novel that I've written, a 142,000 word suspense, was like that. I always knew how it was going to end, until I wrote it. I fell in love with the character who was going to be killed at the end, and found I couldn't kill him. I hadn't expected to love him. He was kind of sleazy after all, but then I delved a little deeper to find out why he was sleazy and once I understood him, I rooted for him.
I'm not saying I did the right thing by not killing him off. If I ever drag the tomb out and decide to rewrite and edit it, I probably will kill him off because the original ending I envisioned is better than the one I came up with to spare him. But I loved discovering new things about him.
In my current wip, a YA, I'm in that discovery mode. I know how the book ends and who the major characters are, but then a new one will show up that I didn't expect, like Caitlyn the Storm, and I discover a new path that the story will take. I love those paths into the unexpected.
BTW, the book from B&N was The White Garden by Stephanie Barron and I did end up purchasing it. I'd love to hear about your unexpected finds, either from your own characters or a book you fell in love with.