Relevant Search : With Examples Using Elasticsearch and Solr
By Turnbull, Doug
Book – 2016
Developers in charge of a search server using ElasticSearch or Solr will want to read this book.
When you are configuring a search server, with thousands or millions of documents indexed, the results should be returned in the order of relevance. But what is relevance, and what if you are not seeing the best order of results? Improve this by tuning for relevance. This process is complex and can be challenging, when you focus on the technical aspects. But you need to work with a domain expert, improve the tuning, check the results, and repeat.
This is the best book available on the subject and is very readable, though it it a bit chatty at the start.