http://oss-docs.addthiscode.net/hydra/latest/user-guide/
They took a bit longer get ready than the code itself, but the pretty
hydra documentation is now part of the open source repo and being
published. Docs are if anything even harder than code, so feedback or
suggestions for them is particularly welcome.
Also if you were wondering what all of those special javadoc tags are
for, your answer has arrived:
http://oss-docs.addthiscode.net/hydra/latest/user-reference/ Some very
cool custom work builds reference docs specifically for each pluggable
type (filters, query ops, etc).