At over 600 pages, this is the largest and most comprehensive book dedicated to Apache Solr. It comprises 16 chapters and three appendices. The chapters are grouped into three sections.

The first section introduces Solr, presents concepts of information retrieval and how they apply to Solr, and covers the installation and configuration of Solr. Moreover, topics related to indexing and analysis of corpora are covered. The second section explores the various features of Solr. It concludes with a chapter that describes the different aspects of deploying Solr in production. The third section covers advanced features of Solr. It begins with a chapter on SolrCloud. This is a set of features that ease running and managing a distributed Solr cluster. The chapter also covers the use of Apache Zookeeper to manage these clusters. The subsequent chapters cover support for handling multilingual text, advanced querying features, and techniques to improve the relevance of search results, thus improving the experience of users issuing searches.

The appendices cover additional ground introduced in earlier chapters. The first appendix has information on working with and contributing to the Solr codebase. The second appendix offers more details for the different languages that Solr supports. The third appendix explores the configuration to import and work with large datasets by using Wikipedia and a dump from StackExchange as examples.

While the size of the book is daunting, it is put to good use by the patient, measured pace and tone that the authors adopt. One of the examples of this attention to detail is shown in chapter 2, which covers downloading and installing Solr, indexing some sample documents, understanding the query form, issuing a sample search, and understanding the results. There is exceptional attention paid to precision when dealing with possibly ambiguous terminology, and there are special notes about the quirks of installing Solr on Windows, along with the judicious use of illustrations. All of this makes up one of the most helpful guides found in a book of this kind.

The book identifies its target audience clearly and does a very good job in explaining details to the average software engineer. Readers not familiar with the concepts of information retrieval are treated just as well as those who are. There is a roadmap for the book at the beginning, along with recommendations on choosing chapters based on what features of Solr one is more interested in.

Overall, this is an invaluable book for anyone interested in learning Apache Solr and putting it to good use. It is also a fine example of a well-written technical book. Although some of the content will likely become out of date as Solr continues to evolve, the aspects of practical information retrieval and the technical insights into clustering, scalability, and availability will make this a useful book to have on the shelf.

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