Writing about art can be challenging. A good place to start is to look at the following book (see link below), particularly pages 77-133. In it, you will find a selection of questions to ask yourself when analyzing artwork.
General books on Asian art, Japanese art, or more specifically, print culture in east Asia can be a good place to begin research as it will provide more detailed information than an encyclopedia entry, but will not spend too much time on one topic. Use these texts and monographs like them to discover themes related to your topic.
The following books are good examples of art books specifically about Ukiyo-e. Some are in Japanese.
Exhibition catalogs can be specific to a museum or gallery and cover an artist's show, a group show, or a given theme. Here are some catalogs that are specific to Ukiyoe prints. Catalogue raisonnés are published in order to list everything a given artist has produced over the course of their lifetime (or part of their life).