Introduction; 1. Finite group schemes Michel Brion; 2. Algorithms for polycyclic groups Bettina Eick; 3. The spread of finite and infinite groups Scott Harper; 4. Discrete subgroups of semisimple Lie groups, beyond lattices Fanny Kassel; 5. Complete reducibility and subgroups of exceptional algebraic groups Alastair J. Litterick, David I. Stewart and Adam R. Thomas; 6. Axial algebras of Jordan and Monster type Justin McInroy and Sergey Shpectorov; 7. An introduction to the local-to-global behaviour of groups acting on trees and the theory of local action diagrams Colin D. Reid and Simon M. Smith; 8. Finite groups and the class-size prime graph revisited Víctor Sotomayor; 9. Character bounds for finite simple groups and applications Pham Huu Tiep; 10. Generalized Baumslag-Solitar groups: a topological approach Mathew Timm.