I use tags for most content-type questions. There are almost always multiple genres: e.g. "Fiction, Science Fiction, Mystery" for a sci-fi mystery, or "Nonfiction, Cooking, Thai" for a Thai cookbook. And there are format tags (nothing for novels, but I have Short Story, Anthology, Poetry, Manual, etc tags). And there's a "Trash" tag for the handful of books I never want to see again.
I have a few virtual libraries: The main one, which excludes books in the others. I'ts essentially all adult fiction. There's a separate one for Children's/YA books. There's one for Recipes/Cooking. One for other non-fiction. And one for Manuals (every time I buy a new TV or blender or printer or whatever, I snag an electronic copy of the manual and put it here).
The tags column is sync'd to shelves on my Kobo reader. I do not sync series to shelves, as it creates way too many shelves to be useful (Kobo shows the series anyway, so I can use that to read the next book in a series).
I realized I never looked at word counts, so I got rid of that custom column.
So I'm left with only 3 custom columns.
- Page count (Uses the Page Count plugin)
- Read (Yes/No) (managed manually)
- Annotations (syncs with kobo annotations using the Annotations plugin)