In this engaging and wide-ranging new book, Nikk Effingham provides an introduction to contemporary ontology - the study of what exists - and its importance for philosophy today. He covers the key topics in the field, from the ontology of holes, numbers and possible worlds, to space, time and the ontology of material objects - for instance, whether there are composite objects such as tables, chairs or even you and me. While starting from the basics, every chapter is up-to-date with the most recent developments in the field, introducing both longstanding theories and cutting-edge advances. As well as discussing the latest issues in ontology, Effingham also helpfully deals in-depth with different methodological principles (including theory choice, Quinean ontological commitment and Meinongianism) and introduces them alongside an example ontological theory that puts them into practice. This accessible and comprehensive introduction will be essential reading for upper-level undergraduate and post-graduate students, as well as any reader interested in the present state of the subject.