All year I’ve referred to “Sarah & Katy and the Book of Blank” as the sequel to “Sarah & Katy and the Imagination Blankets.”

All year, I’ve been uncomfortable with that definition.

While Book of Blank takes place in the same general time and setting of Imagination Blankets, each book stands alone. Book of Blank doesn’t build upon Imagination Blankets like a sequel would; it simply takes Sarah’s and Katy’s characters on a new adventure.

Aside from Sarah and Katy, no recurring characters appear in the second book. We don’t meet Bast, Jelani, Ruddy, or Destrian Wain again. (Much to my nieces’ disappointment … they’ve already wrangled that information out of me and aren’t pleased that I’m not bringing back their favorites.) Instead we get a host of brand new characters. And no references are made to the events of Imagination Blankets (except one allusion to Katy losing her shoe).

It seems disingenuous to call Book of Blank a sequel when I know it’s a standalone book. It also feels incorrect to call it Book 2, because at this stage I’m not sure I will build Sarah & Katy into a full-fledged series (although I want to keep the option open).

That’s why I was relieved this morning when I read Lisa Graff’s blog post, “The Case for the Companion Novel,” at Nerdy Book Club.

Companion novel. That feels like the genuine and correct classification for Book of Blank.

The two books clearly are linked, but it’s a loose connection. Dubbing Book of Blank as the companion is the perfect definition.

And now that classifying the book is out of the way, I suppose it’s time to finish book production. The book release date is one month from this Saturday; my emotions are a blend between “Hooray!” and “Yikes!”