In The Fourteenth Goldfish (Random House, 2014), Jennifer Holm introduced a story with a unique blend of genres: call it contemporary fantasy, grounded in the principles of scientific inquiry. Now the author, who has won three Newbery Honors for her historical fiction novels, follows Goldfish with a sequel, The Third Mushroom, which continues the exploits of Ellie, 12, and her grandfather, Melvin, who is… 14. (The anti-aging properties of jellyfish are involved.) We spoke with the author from her home in California.

You are considered a master of middle grade historical fiction. Why the switch to contemporary stories?

Well, the research I had to do for these books was a little bit like doing the research for historical fiction, digging into all the scientists’ backgrounds—Galileo, Salk, Oppenheimer—and looking for those moments in their lives that readers could connect with. It also felt a lot like history to me because a lot of it came from remembering my dad, who was a doctor. He was a much older father. He ran away from the farm and joined the Navy. He piloted jets off aircraft carriers during the Korean War, and then became a flight instructor. He used the GI Bill to go to medical school and it was only then that he had a family. He was interning by the time I was born.

Did his interest in science spark yours? Were you a science geek as a student?

There were always discussions at the dinner table about things like polio and microbes and penicillin. And I had a couple of great science teachers. I loved my science teacher in sixth grade, Mr. Jones. I had a crush on him. He was young and funny. He would give us mimeographed handouts on which he had drawn funny little cartoons in the margins—doodles of mitosis. I don’t remember any other teacher doing that and it went into Holm Imaginative Vault. And I had a teacher senior year in high school who really knew how to make science come alive. This was back in the day when teachers used to wear a lot of decorative pins—this is sounding like historical fiction, too—and she would tie a big ole insect to her pin. She was kind of wacky.

Melvin, the grandfather in this series, is such a great character. Somehow, even though he is cranky and truculent, he is lovable. Is he based on anyone?

Now we’re back to my dad. Melvin is definitely inspired, at least a little bit, by my dad, who had very fixed ideas about certain things but was also very interested in science. He would keep petri dishes of things like blood agar in the refrigerator. The whole time I was growing up I thought everybody’s dad grew bacteria in the fridge. I was shocked to learn differently when I got to college. We also had a linen closet that was literally stocked with samples from pharmaceutical companies.

Your kids are now the age of your readers, right? Do they give you feedback?

Will is 14, about to be 15, so he’s kind of lost interest, but Millie is 11 and she is still interested. Her class read The Fourteenth Goldfish and she was able to point out all the inside jokes. She’s also very much interested in science so she’s a good influence on me.

And finally, a fifth question but we have to ask: Ellie overcomes a strong aversion to mushrooms. Are you anti-mushroom, too?

I hated them when I was a kid but I like them now. My kids won’t eat them at all.

The Third Mushroom. Jennifer L. Holm. Random House, $16.99 Sept. 978-1-5247-1980-7