Who this book is for
This book was written for Elasticsearch users and enthusiasts who are already familiar with the basic concepts of this great search server and want to extend their knowledge of Elasticsearch. It also covers topics such as how Apache Lucene or Elasticsearch works, along with getting aware of the changes from Elasticsearch 1.x to 5.x. In addition to that, readers who want to see how to improve their query relevancy and learn how to extend Elasticsearch with their own plugin may find this book interesting and useful.
If you are new to Elasticsearch and you are not familiar with basic concepts, such as querying and data indexing, you may find it a little difficult to use this book as most of the chapters assume that you have this knowledge already.