Stories told in two books

[Dark Muse]

There is this author I really like, and he always writes in his books in pairs. His books always come as a set of two. And so this made me curious. Does anyone know, is there actually a technical term to describe a story consisting of 2 books, the way in which 3 books in a story is called a Trilogy.

[Erichtho]

Dilogy.

[Dark Muse]

Ahh, thank you much

[tractatus]

Dilogy / Duology.

I ve heard second one mostly, yet it s not common used as trilogy.

[JBI]

potboiler. Just kidding. No, usually you just call it the first book, and the sequel.