Currently policy is generally that all individual works get their own individual tag. Some exceptions apply, such as films or books of a series (similar to how each episode of The Expanse will not get its own tag). So, there's not a need to tag Caliban's War individually, which Gallifreyan's answer also addresses, unless the question is truly about events self-contained within those books or the book itself (such as writing it, behind the scenes, analysis, etc.).
Some pre-existing popular tags, like Harry Potter, do not have a book and film distinction because they have been grandfathered in due to the sheer magnitude of work involved in adjusting the tags. But, in general, we shouldn't penalize a written work because a TV or film version of it happened to be produced without changing the title Legend of the Seeker or Game of Thrones style.
The general format is the original media gets the plain tag:
And the same named works in whatever media get the initial year of release appended to the end, so the TV series would be:
That is what I would normally recommend doing in case there's already questions about one or the other (or a question about both and adaptation-comparison.
However, to make it more clear, I would prefer the-expanse-novels and the-expanse-2015 to avoid mistagging show questions with the book tag.
In order to accomplish this with the least disruption, we need to:
- Figure out which questions are about which work (TV vs Books vs Both)
- Likely get a moderator to rename the tag of the largest group
- Manually (over time) remove the old and add the new tag to the other group