If Rick Riordan could be any ancient god from any pantheon, he’d choose Hermes.

“He’s the god of travel, which I love to do, and a jack-of-all-trades who’s into a lot of cool things,” said Riordan, author of the popular “Percy Jackson” young-adult (YA) novels. “I’d love to take his job for a day.”

Hermes is an apt choice. As messenger to the Greek gods of Mount Olympus, he moves easily between the worlds of the mortal and the divine. So does Riordan, in his imagination at least, and he’s taking millions of readers along for the ride. More than 35 million copies of books from his five series — four YA and one adult mystery — are in print. Two Disney movies have been adapted from the first two books of the first series, “Percy Jackson and the Olympians,” about a teen who discovers he’s a descendant of Poseidon.

Minneapolis YA author Will Alexander, who last year won a National Book Award in the category for “Goblin Secrets,” said Riordan’s tales appeal to young readers because “kids lead mythic lives. Their world is run by the arbitrary whims of titanic people. Myth logic makes perfect sense under those circumstances.”

Riordan will be in town Tuesday for a Talking Volumes event at the Fitzgerald Theater, the last stop in only eight he is making in the United States for his latest book, “The House of Hades.” We recently caught up with him by phone from Boston, where the San Antonio native moved a few months ago with his wife, two sons, a basenji/terrier mix named Speedy and three black cats.

Bedtime-story beginnings

Spinning yarns is in Riordan’s DNA. When he was growing up as an only child, his mother helped him build that skill by “encouraging us to tell round-robin stories as a way to keep busy during car rides or on campouts. She would start a story with one sentence, and I would have to think up the next one, then an aunt or uncle or cousin, and so on. There’s a strong tradition of oral history in Texas hill country. We never let reality get in the way of a good story. The Western tall tale owes a lot to mythology, so making up my own made sense on an intuitive level.”

After graduating from the University of Texas at San Antonio in 1986, Riordan taught history, English and, yes, Greek mythology at various schools in that area and San Francisco for 15 years. But it was the challenge of coming up with an ongoing bedtime story for his older son Haley, then 8, that first brought Percy Jackson to life.

Haley, who had an intense interest in myths, has been diagnosed with dyslexia and ADHD. Riordan came up with the idea of a tween boy hero “as someone for my son to relate to.” Haley, now in his first year of college with authorial aspirations of his own, insisted that Dad start writing them down, and the “Heroes of Olympus” were born.

Why so popular?

Homer didn’t inject many one-liners in his original tales of the gods, but laughs are a big part of what makes Riordan’s books so popular — as well as word choices Homer never would have dreamed of, such as “sucktastic” and “Old Seaweed” as a nickname for Poseidon.

“Humor is as critical to a good story as spice is to a good dish,” Riordan said. “I put a funny spin on things, but I try to be faithful to the original structure and keep the relationships of the characters the same as they would have been.” Handy glossaries at the back of each book help readers keep all those gods straight, but a lot of young readers don’t need it, he said: “They soak it all up like a sponge. It’s the adults who need reminders.”

A lot of Riordan’s fans were driven crazy by the literal cliffhanger at the end of his last book, when Percy and his pal Annabeth tumbled off a precipice toward the Underworld. “I love and hate Rick Riordan,” wrote one fan on a blog. “I love him for writing the books, and I hate him for leaving out the best part. He’s so evil.”

“I never bow to pressure not to be evil,” he said, laughing. “That reaction is an important sign you’re doing something right. I was like that as a teacher, too. I would intentionally leave kids hanging on a story so they would look forward to the next class instead of dread it, and they would all groan.”

Riordan is near the top of the crowded list of authors who have tried their hands at YA fiction since the runaway popularity of a certain bespectacled student at Hogwarts School of Witchcraft and Wizardry. According to Nielsen BookScan, sales of YA fiction — classified as targeting readers age 12 to 18 — have jumped nearly 150 percent in the past six years.

“The wild success of Harry Potter didn’t just open a door in the literary marketplace for fantasy — it opened wide the floodgates,” said Mary Rockcastle, creative-writing director at Hamline University, who in 2007 launched an MFA program in writing for children and young adults.

As with most masters of a craft, Riordan makes writing YA look easier than it is. But Rockcastle points out that Riordan was a successful writer of adult mysteries, including the Edgar-winning “Big Red Tequila,” before taking a dip in the YA pool.

“He already knew how to tell a fast-paced story, create characters worth caring about and develop a vivid, believable world on the page,” Rockcastle said. “Add to that his own experience as a parent and middle-school teacher with a fascination for mythology, and you’ve got a winning combination.”

As a byproduct of his work, Riordan said, he has enjoyed doing his bit to keep the Greek and Roman classics relevant.

“I’ve had professors tell me a lot of students are coming to class armed with a lot more knowledge than they used to, and the kids thank me for helping them pass their exams,” he said.

Next on his plate: the Norse gods.

“They’ve influenced everything from Marvel comics to ‘Lord of the Rings,’ ” he said. “Those characters have always been close to my heart.”

Move over, Mercury and Athena. It’s time for Riordan to dust off Odin, Thor, Loki and Freya for their moment in the YA spotlight.