Exploring ElasticSearch: A human-friendly tutorial for ElasticSearch. by Andrew Cholakian.
An incomplete tutorial on ElasticSearch.
However, unlike printed (dead tree) and pdf (dead electrons), you can suggest additional topics and I suspect that useful comments would be appreciated as well.
A “live” tutorial on popular software like ElasticSearch, that follows the software as it develops, could prove to be almost as popular as the software itself.