What I really miss from the official docs is a reference. Something that lists all endpoint sand gives a pseudo-BNF schema overview. With the current docs, seeing all the possible permutations possible within the JSON structure is left as an exercise for the reader; it really requires reading the descriptions of the APIs very closely.
This guide is pretty good and gives you a comprehensive view of Elasticsearch, but to me it was a bit confusing when I first read it. If you are looking for a more "tutorial" style book, with some examples and use-cases, I would recommend "Elasticsearch in action"[0].<p>I might be biased towards Manning books, but I find their style and ELI5 wording to be very helpful as an introduction to a subject.<p>[0] <a href="http://www.manning.com/hinman/" rel="nofollow">http://www.manning.com/hinman/</a>