First of all, I love the illustration of Hazel on the cover and the fact that it seemed to be a pretty accurate representation of how she actually looks. But, the book isn't about the cover, so we'll talk about the actual contents.
The main focus in Breadcrumbs is Hazel's growth when it comes to "growing up." Everyone's always telling her to get used to the real world and that everything isn't as magical is she likes to think. I appreciated that Hazel could see perfectly well that everyone was telling her to grow up, but she refused to give up on the things she believed. And in the end, Hazel certainly learns some things and grows a little, but she doesn't just drastically change and become all adult-like, which is good.
The forest was interesting. There wasn't really any rhyme or reason (as far as I could tell) to what happened or showed up in the forest which made it feel kind of weird, but not necessarily in a bad way. The forest characters were interesting and kept me guessing, which I enjoyed.
Generally, I don't read a lot of contemporary middle grade. I mostly read fantasy/adventure and the like, but Breadcrumbs managed to get the perfect balance between contemporary and fantasy. The main conflict is Jack growing away from Hazel which is a fairly contemporary type of thing, but Hazel also goes on a quest to save Jack from a witch (through a forest) that is decidedly fantastical. Ursu kept me entertained while also dealing with a very real thing almost all of us go through at some point in our life.
The Nutshell: Breadcrumbs is a great contemporary-fantasy hybrid and I highly enjoyed it. It was a quick read that kept me engaged throughout the story.