Geany's documentation is available in different formats.
HTML and text versions of the documentation are installed when you install Geany. Choose the Help->Help menu item to view the HTML version. The manual will be opened in a browser window (unless the browser command is not set correctly in the Tools tab of the Preferences dialog).
You can also read the manual online:
Current Manual in HTML format
Current Manual in TXT format
0.19 Manual in HTML format (Russian)
This documentation contains the most recent changes in Git, and will probably include some features not in the current release.
Online Manual (updated nightly from Git)
Manual in TXT format (updated nightly from Git)