It must be a mixed blessing winning a Newbery Award for your first novel, like Clare Vanderpool did with this one in 2011. I imagine it is very possible she'll grow as an artist and craftsperson and write better books that will probably have no chance to win. Another downside is that some readers will see that it won a Newbery and will judge it too harshly. Not me. I rounded up to 4 from 3-plus because this is a very good first novel. It has a lot going for it. I also think it is very possible many members of its target audience will love it and be changed by it. Don't trust anybody over, what, thirty? Anyway, if you're a tween or slightly older, don't trust me.
Some of the many things this book has going for it: an intricate plot with a frame story and multiple mysteries that connect the two stories, mysteries that connect objects and events across time; big themes such as the meaning of home, family, memory and story; history (one plot takes place in 1918 and touches on labor issues, World War One, immigration, and an influenza epidemic; the other plot takes place in 1936 and touches on the Depression and hobos); a likable girl narrator who is a bit of a tomboy; adventure, including boy characters who are featured in the 1918 plot; an ending powerful enough to choke me up.
Here's one area where I think the book falls short, especially (grouse, grouse, grouse) since it won a Newbery: Clare Vanderpool is good at differentiating between characters and creating voice, but I did not feel most of the characters were fully realized or that the voice was convincing enough, especially for the narrative that took place in 1918, a big problem because the author was being very ambitious and trying to give voice to a whole community, a community of immigrants. Abilene, the novel's main character and the narrator of the 1936 story, however, was a notable exception. Her portrayal was not flawless, but it was very good.