The Little Sisters of Eluria is a short novel of about 80 pages. It takes us back to a time when Roland was still on the trail of the Man in Black
, long before we first meet him in The Gunslinger. As far as I know, Little Sisters will not be Part of Dark Tower V
, and it's uncertain if it will ever make into any of the forthcoming novels.
Personally, I find this unlikely because I don't see how it could fit into the storyline, assuming we will be learning more about the future of Roland's quest (i.e. following the main plot) in the next installments, instead of further flashbacks to the past. Also, since King seems to be tying more and more of his works to the Dark Tower saga (at the latest, Little Sisters connects Desperation
to Roland's World), it would seem quite reasonable to see more closely related stories like Little Sisters appear out of the line of the Dark Tower Books.