mine too !!!! .. isn't it a collaboration between 2 authors ?
Well, the "world" is a collaboration. Steven Erikson wrote all the (10) books in the Malazan Book of the Fallen series. About half-way through the other guy, Ian Esslemont, started publishing his own books in the same world. This was, AFAIK, the plan all along and I have no idea on when the books were actually written or anything. Esslemont's books are supposedly completely consistent with Erikson's books, so there has clearly been a lot of collaboration. The books themselves are not collaborations, though.
I haven't read any of Esslemont's books. Not sure why. I think I definitely need to put at least one on my reading list.
Esslemont's books, by the way, seem to take unexplored (or under-explored) aspects of the main series and tells that part of the story. For instance, his first book is the story of what happened that night of the "regime change". His second book is the story of the Crimson Guard after Esslemont's books.
As such, it doesn't seem like Esslemont's series constitutes an "epic series" in the same sense as Erikson's, but more a collection of disparate books (that I imagine are quite readable in any order, but recommended after the main series) taking place in the same world.