Sometimes you know what something is by what it isn’t. That’s the logic used by Maine author Wendy Ulmer in her charming, whimsical new children’s book, “A Isn’t For Fox: An Isn’t Alphabet,” lushly illustrated by Laura Knorr and out now on Sleeping Bear Press.

Ulmer, a former English and music teacher, lives in the town of Arrowsic, across the river from Bath. “A Isn’t For Fox” is her second book for children, after “A Campfire for Cowboy Billy.” The new book has simple but vivid imagery – “P isn’t for goats; it isn’t for boats/P is for possums in warm, furry coats” – is easy for even the littlest readers to say, while teaching them their ABCs and beginning reading skills.

Ulmer will appear at Borders in Bangor at 2 p.m. Sunday, April 6, where she’ll sign copies of her book and read aloud. The Bangor Daily News spoke with her last week.

Where did you get the idea to teach children the alphabet in this way?

I was teaching freshman English at Morse High School in Bath. My freshmen weren’t using much detail in their stories. I thought, “Let’s go out of the box, and look at it in a different way.” I asked them to write three paragraphs of description, in which they have to describe everything by what it wasn’t. So it became “The boy who was not wearing sneakers was not chasing the girl with freckles.” It made them think differently.

Then later, I was having trouble focusing in a meeting, because I kept thinking about that idea. Then, all of a sudden, “A isn’t for fox” was in my head. I kept playing with that for two years, until I had the whole alphabet done. My best friend told me to submit it for publication.

What’s one of your favorite rhymes in the book?

I love the idea of the octopus having to knit all those socks at the same time. And the illustrations [by Laura Knorr] are just wonderful. It’s a really beautiful marriage of pictures and words.

What do kids respond to, when they read the book?

When I read it to them, I leave out the actual thing that it is. I’ll read, “A isn’t for fox, or box,” and leave the other part blank, and they love to be able to name what it is. And some of them don’t know what a gecko or iguana is, so it’s fun for them to look at it and figure out what it is. Sometimes I’ll stop and say, “Do turtles wear bow ties?” and the little ones will have to stop and think about it. The second-graders will say “No, that’s silly!”

Are you working on any new books?

I’m working on some things. I don’t have another contract yet, but I’ve had some fabulous rejection letters!