I loved the twin relationship in the book, too, both for the fraternal twinness and the sibling interaction/support. And, I liked the book enough to seek out her first book, which I have just finished.
As for The Art of Forgetting, I had more difficulty getting caught up in the story. I've known a number of people with head injuries (enough so that I wore a helmet riding my bike long before it was fashionable or easy to find.) I've experienced first-hand the subtle and not so subtle changes that can occur in an injured brain (someone else's, not my brain, though at times I've wondered if I was the damaged one,beefing the world in a weird slant because of the vehemence of reactions thrown my way.) it's hard, truly. But my issue with the book is that the peri jury relationship between Marissa and her best friend Julia had weird pathologies without a brain injury. There were a few moments I really liked (like the conversation about swans never forgetting wrongs done them, as opposed to human, who do, which led to the title of the book), or some of the ways the author chose to exacerbate and explore conflict and resolution.
I'll keep my eye open for future books by this author.