I'm always reading something, usually multiple books at a time.
I tore through this book. Although I liked the first book (solid three stars = GOOD in my system), this book had me riveted. Warcross sets the stage, and Wildcard digs into the most interesting bits.
I mentioned at the end of my review for Warcross that the big reveal near the end of the book did not take me by surprise, but that did not diminish my enjoyment--and it still left many questions to be answered (there is a major mystery at the center of this book).
Marie Lu has tweeted that the two books are a duology--so there is no third book to watch for. I would recommend that interested readers think of the two parts as one big book--make sure you have them both before you get started, so you can jump right into Wildcard after you finish Warcross. Gaming, virtual reality, and thorny questions about free will vs. control lie within.
There is a bit of the familiar YA trope of a teenage girl being thrust into a role where the fate of the world lies in balance, depending upon her actions--but that wasn't a deal-breaker for me.