Exactly, my mind was blown when I read Six of Crows. The author nailed that series.
I was worried that I might not like Shadow and Bone like you said the background was very lightly written but I like any book that manages to grab my attention and I forget to put it down. It was like that with this book despite the few shortcomings. 😀
Glad to found somebody who knows the Grishaverse. 😍