Note: Sorry in advance, but I have difficulty writing when working on the same book's chapters sequentially.
Keygemin is a series of books that does not share story or characters between them, but is set in the same world during the same period of time.
Within is a chapter named "Blurbs" which contains the blurbs for each book. There are also the "Series Prologue" and "Glossary" chapters, which give detailed information about the universe.