The Geneva library is fully documented in the Geneva Manual. This book is constantly being improved and updated for the latest Geneva version. It already contains a whooping 350+ pages! This manual is covered by the Creative Commons "Attribution-Noncommercial-No Derivative Works 3.0 Germany" license, it is freely available but you may not alter, transform, or build upon it, nor use it for commercial purposes.
Likewise, the Geneva reference manual is available here. It was created using Doxygen directly from the Geneva sources. NOTE: do not print the reference manual, as it has over 5000 pages!