The Concise Oxford English Dictionary defines a fidus Achates as 'devoted follower, henchman'; and one of the aims of this Companion is to be as helpful as possible to its readers. It is devised for anyone, whether a classicist or not, who is seeking guidance and orientation for a fuller understanding of Virgil. We have assumed that most of those who consult this volume will have read parts of Virgil's poetry if only in translation - for those with Latin the best introduction is to read some of the texts with a good commentary, of which there are many. We certainly cannot attempt to replicate the work of the commentators here; rather we offer a series of essays on topics which can constitute useful entry-points for the devoted student of Virgil. And though we aim to help and to provide what is sometimes called 'basic information', we do not seek to simplify or to offer any sort of bland orthodoxy. We assume that our readers (even if not expert on the subject) are seeking intelligent and sophisticated comment, and we hope that the book will prove exciting as well as useful, and will point to the shape of Virgilian scholarship and criticism to come.