This book is amazing. The basic plot is that in 2019 we detect radio signals from a nearby system. The Jesuits decide to mount a private expedition. In 2060, one survivor returns. The question is then: what happened? The author manages to interweave two narratives - the past and the present - seamlessly. She builds suspense, dropping tiny hints about what happened, slowly revealing the horror they experienced. Along the way we must deal with heavy philosophical problems: what is God's will? What is our purpose? How do we deal with an entirely alien civilization? What if our actions have unforeseeable consequences?
I found this book to be completely absorbing, and I was very sorry to finish it. Of course, I have learned there is a sequel, which I must get my hands on as soon as possible.