We all know what irritates Darth Vader: Sand. (Can’t blame him on that one; it does get everywhere.) But what scares Darth Vader? Thanks to author/illustrator Adam Rex’s charming new book Are You Scared, Darth Vader?, we now know.  And it’s not what you might think.

The author recently sat down with the folks over at io9 to talk about the book, its Star Wars origins, and how he felt when Lucasfilm first approached him about writing a Star Wars story.

Rex, like me, was four years old when Star Wars (pre-A New Hope-designation) hit theaters in 1977. Also like me, Rex fell in love with the franchise early on and carried that love through to adulthood. So, when offered the opportunity to write a Star Wars children’s book, he didn’t hesitate to accept. The task wasn’t an easy one, however, as he suggests to io9:

As an idea, it had one of those unsatisfying origin stories where I think the title came to me while waiting at a stoplight and I sat down to figure out what kind of book might have a name like that.”

The result is a story that teaches children about fright with the most fearsome character in Star Wars, Darth Vader, as the central character; Rex does so in a delightfully playful way, however, utilizing the writer’s dry sense of wit to dive into Vader’s fears.

In the book, the usual, spooky suspects tease and taunt Vader in an effort to find out just what might frighten the Dark Lord of the Sith: there’s a wolfman, vampire, ghosts and ghouls galore. But how does such a story tie in to the rest of Star Wars canon? As Lucasfilm’s executive director of publishing Michael Siglain described to io9, it doesn’t.

“With direct film tie-ins,” he explained, “publishing strives to make sure those titles enhance, support, or retell the films in exciting and dramatic ways.” When it came to Are You Scared, Darth Vader?, however, Rex wasn’t so constrained. “With books not directly tied to the films, but tied to the larger saga, we have opportunities for new and different approaches to the stories we can tell.”

So just what does scare Darth Vader? You’ll have to read the book to find out. It’s available now in electronic format and in hard copy at retailers everywhere.