K3 surfaces and their moduli form a central topic in algebraic geometry and arithmetic geometry, and have recently attracted a lot of attention from both mathematicians and theoretical physicists. Advances in this field often result from mixing sophisticated techniques from algebraic geometry, lattice theory, number theory, and dynamical systems. The topic has received significant impetus due to recent breakthroughs on the Tate conjecture, the study of stability conditions and derived categories, and links with mirror symmetry and string theory. At the same time, the theory of irreducible holomorphic symplectic varieties, the higher dimensional analogues of K3 surfaces, has become a mainstream topic in algebraic geometry.

Introduction.Samuel Boissière, Andrea Cattaneo, MarcNieper-Wisskirchen, and Alessandra Sarti: The automorphism group of theHilbert scheme of two points on a generic projective K3 surface.- Igor Dolgachev: Orbital counting ofcurves on algebraic surfaces and sphere packings.- V. Gritsenko and K. Hulek: Moduli of polarized Enriques surfaces.- Brendan Hassett and Yuri Tschinkel: Extremalrays and automorphisms of holomorphic symplectic varieties.- Gert Heckman and Sander Rieken: An oddpresentation for W(E_6).- S. Katz, A.Klemm, and R. Pandharipande, with an appendix by R. P. Thomas: On themotivic stable pairs invariants of K3 surfaces.- Shigeyuki Kondö: The Igusa quartic and Borcherds products.- Christian Liedtke: Lectures onsupersingular K3 surfaces and the crystalline Torelli theorem.- Daisuke Matsushita: On deformations ofLagrangian fibrations.- G. Oberdieck andR. Pandharipande: Curve counting on K3 x E,the Igusa cusp form X_10, anddescendent integration.- Keiji Oguiso:Simple abelian varieties and primitive automorphisms of null entropy ofsurfaces.- Ichiro Shimada: Theautomorphism groups of certain singular K3 surfaces and an Enriques surface.- Alessandro Verra: Geometry of genus 8Nikulin surfaces and rationality of their moduli.- Claire Voisin: Remarks and questions on coisotropic subvarietiesand 0-cycles of hyper-Kähler varieties.