There's no harm is reading 'Trace' first, its just a shame she's changed so much.
I will say this, that if you don't enjoy the book, please try her earlier ones they are brilliant, its not that 'Trace' is total rubbish, its just that compared to her earlier stuff is it a letdown, she 'waffles' a bit more, almost as if she is trying to fill the pages up.
I am still going to reread it so I can discuss the book with you guys, though I'll probably skim through it rather than read every page