Springer Handbook of Spacetime published on 7 July 2014 (see Amazon)
From Illusions to Reality: Time, Spacetime and the Nature of Reality (Minkowski Institute Press, Montreal 2013) published on 8 September 2013Inertia and Gravitation: From Aristotle's Natural Motion to Geodesic Worldlines in Curved Spacetime (Minkowski Institute Press, Montreal 2012) published on 18 December 2012
Hermann Minkowski, Space and Time: Minkowski's Papers on Relativity (Minkowski Institute Press, Montreal 2012) published on 27 August 2012 (ebook) and on 6 December 2012 (softcover on Amazon)
Free version: PDF and at Apple's iBookstore
Hermann Minkowski's paper "Raum und Zeit" (Space and Time) in German and English [choose Front Matter - Download PDF (512KB)]