I haven't read Katerina's Wish, but I think Wonder would be a wonderful first selection. Just a heads up, though, that I'm in a faith-based book club and have pitched reading it and others are reluctant. I think it's because they're dismissing it as a children's book... We've read YA before, so I'm not sure what the deal is. I'm still hoping to change their minds because I think we'd have a great discussion about it.
Another excellent book for a church group would be Marcelo in the Real World by Francisco X. Stork.
Also, a great source for book ideas is shereads.com. Although the books aren't explicitly "Christian" fiction, they tend to have components that lend easily to looking at them from a faith-based perspective. My favorite of the ones that we've read from their recommendations is Vanessa Diffenbaugh's The Language of Flowers.