First of all, I must declare self interest: Blast Theory's work features heavily in this book. That said, this is a rare and insightful book combining expertise in theatre and presence (Giannachi) with that of computer science and human computer interaction (Benford). What they have achieved through this combination is an integrated understanding of how arts and sciences are combined in mixed reality performance. It uses indepth interviews with various practitioners to bring the projects to life and to embed the study within the reality of artistic practice. The book covers Brendan Walker's work on studying thrills and a ground breaking location based education project called Savannah. And it finishes with a powerful argument for the use of 'trajectories' as a way of conceptualising live interactive works.