Formal:
* Decalogy: This is the most accurate term for a 10-book series. It comes from the Greek words "deka" (ten) and "logos" (word).
* Ten-book series: This is a straightforward and descriptive option.
Informal:
* Series: This is a general term for a group of books that are connected by a common theme, characters, or setting.
* Saga: This term often implies a long and epic story, but it can be used for any series with a strong narrative arc.
* Cycle: This suggests a cyclical pattern or recurring themes within the series.
* The [Name of Series] series: Many series are named after a prominent character, theme, or location within the books.
Ultimately, the best way to name a series of 10 books depends on the specific content and style of the books. Consider what is most descriptive and memorable for your target audience.