As I understand it the Omnibus only collects the first five installments which got published as independent short stories originally (although only one of them is actually self-contained, the rest build on one another).
The story is fairly closed by that, or at least the main characters arc is brought to a more or less satisfying end, however, for the whole story you need to read the further two (?) books.
The story is fairly closed by that, or at least the main characters arc is brought to a more or less satisfying end, however, for the whole story you need to read the further two (?) books.
This edition seems to contain the whole series:
https://www.goodreads.com/book/show/2...