See, this is why one shouldn't procrastinate writing the review of a book until long after one has finished reading it. I read Graceling over the winter, and then a few weeks later I read Fire, and then Bitterblue, and then Winterkeep. I actually currently have Seasparrow checked out of the library. It's on the floor beside my reading chair, in an untidy pile of books and also the lap blanket that I knit out of my very first attempt at spinning yarn. The first three were re-reads, but Winterkeep and Seasparrow are new to me. I'm fond of all of them, although I do think Bitterblue might be my favorite.
All of the Graceling books are about dysfunctional families and lies and how to survive them and then keep living. Fire is quite different than Graceling but the resonances match. There is, of course, the appearance of Leck to tie them together, but also Fire's father, who loved her and tried to mold her into a monster like himself. And of course the only way to escape a man like that is to cut your way out.
I don't know about Cashore's motivation for writing these things, but I know my motivation for reading them. It doesn't even have to be that bad, to leave a mark.