Literary Fiction: in a subplot involving a minor character, a statue of the Infant of Prague is brought back to the US by a soldier who got it in Europe during WWII.

[Heidi]

The soldier is weirdly attached to the statue, which comes to make sense later when someone discovers something that has been hidden in the statue for a long time,

I don't remember what was found or why it was important, or even the main plot of the book. Whatever is found inside the statue of the Infant of Prague ends up being significant to the main story, in a small but necessary way. It's a book with lots of threads in it that come together at the end, sort of in the style of John Irving's writing. I read this book within the last 5-10 years, I think.

[Kris]

A longshot - The Bone Church by Victoria Dougherty?

Google search of Goodreads:
site:goodreads.com fiction ww2 "infant of Prague"

Note: Also referred to as The Infant Jesus of Prague.