You can publish almost anything.
Journals.
Planners.
Workbooks.
Guides.
Poetry.
Short stories.
How-to manuals.
Coloring books.
Recipe collections.
Fitness logs.
Budget trackers.
Devotionals.
Prompt books.
Educational activity books.
There are thousands of categories and sub-categories. Fiction. Nonfiction. Low content. No content. Niche topics. Hyper-specific interests.