Voyage is a small persistence framework developed by Esteban Lorenzano, constructed as a small layer between the objects and a persistency mechanism often a document noSql database and this is a booklet describing its usage and operation.
Browse the directory for released versions of the booklet or look here for more Books and Booklets
You can find the PDF at https://ci.inria.fr/pharo-contribution/job/Booklet-Voyage/ The result from the latest successful Travis build can be found on Bintray (PDF).