Laurie Halse Anderson is one of my favorite authors; Speak and Wintergirls both changed my life. Oliver's style is in some ways very similar to Anderson's. I think this book is every bit as good as Anderson's, and that is a massive compliment coming from me.
If you're not pre-ordering this now, you should read my (no-spoiler) review of the book. It still has me thinking three weeks after I read it, and I think I'm going to re-read it this week. Yes, already.