This book does a very good job of introducing, clearly and concisely, key definitions, concepts and foundational results, necessarily leaving much of the detail to exercises and references, while also giving a flavour of current research . It seems very much suited to its original target audience, but others, even those like me who couldn't be bothered doing the exercises, will find it an enlightening read, and will benefit from the well-judged choice of topics. (Neil P. Dummigan, Mathematical Reviews, December, 2019)