Brad Meltzer’s fans know him for conspiracy-heavy political thrillers like “The Inner Circle” and “The Fifth Assassin.” His most recent blockbuster, published last month as “The President’s Shadow,” begins in the White House Rose Garden with a gruesome discovery: a dirt-encrusted severed arm, buried beneath the manicured grounds.  “The President’s Shadow” isn’t Mr. Meltzer’s only recent work to begin in a garden. Another new book of his also opens among flowers—though they’re illustrated, candy-colored and accompanied by a smiling cartoon drawing of Helen Keller, her arms spread wide with joy.  “I Am Helen Keller” will be the seventh installment in Mr. Meltzer’s “Ordinary People Change the World” series, a collection of short, illustrated biographies for children he pens on breaks from his dark thrillers. To be published in September by Dial Books for Young Readers, “Helen Keller” gives a simplified account of Keller’s life in bright, comic-strip-like panels. “I am Helen Keller and I won’t let anything stop me,” the book reads, as a child-sized Keller leads a group of children through a field of wildflowers.  The children’s biographies pose a sharp contrast to Mr. Meltzer’s thrillers, which have sold more than 10 million copies in the U.S. His popular “Culper Ring” novels, of which “The President’s Shadow” is the third, imagine that a secret spy ring, founded in real life by George Washington, continues to exist today. His 2013 novel, “The Fifth Assassin,” follows a killer bent on re-creating presidential assassinations. He’s also the host of two History Channel television shows, “Brad Meltzer’s Lost History” and “Brad Meltzer’s Decoded,” and the author of several comic books.  He’s making headway with his younger fans. The “Ordinary People” series, which launched last year, has more than 600,000 copies in print and has had three bestsellers. “Helen Keller” will follow the July 14 publication of “I Am Lucille Ball,” which features a bright pink cover decorated with a large red heart, and scenes of Ball pretending to be, variously, a pirate, a pelican and a frog. The lives of other famous figures, including Rosa Parks, Albert Einstein and Jackie Robinson, are similarly colorful and upbeat. Amelia Earhart builds a roller-coaster in her backyard. Abraham Lincoln saves a group of turtles.  Mr. Meltzer, 45, writes in a secret room he built inside his Fort Lauderdale, Fla., home. He said the children’s books grew out of a shopping trip he took with his daughter three years ago. “All I could find were clothes with princesses on them,” he said. “I was tired of my own kids looking at reality TV show stars and thinking that’s a hero…I said, ‘I have so many better heroes in history that I can give them.’”  He pitched the books as a collectible series illustrated by his friend, comic-book artist Christopher Eliopoulos. Mr. Meltzer had had success with two books along similar lines, “Heroes for my Son” and “Heroes for my Daughter,” but he wanted to write an ongoing “library.” “We never said we want to do ‘Amelia Earhart’ or ‘I Am Abraham Lincoln,’” he said. “We said we want to do 60 of these.”  The author says his thrillers and his children’s books grow out of different sides of his brain. But sometimes they overlap. Mr. Eliopoulos often sneaks drawings of Mr. Meltzer into the background of scenes—on a crowded bus with Rosa Parks, for example. On other occasions, he has hidden the name of the protagonist of the author’s “Culper Ring” novels, Beecher White, among the illustrations.  Mr. Meltzer finds connections between his disparate works as well. Both his thrillers “The Inner Circle” and “The President’s Shadow” reference George Washington’s use of invisible ink, a fact that will appear—illustrated—in the forthcoming “I Am George Washington.”  Mr. Meltzer’s literary side project is one of a number of children’s series rooted in history to take off in recent years. Scholastic’s “I Survived” series, which focuses on devastating events like Hurricane Katrina and the bombing of Pearl Harbor, has more than 13.8 million copies in print in the U.S. The covers of Grosset & Dunlap’s “Who Was…?” biography series, which has more than 18 million copies in print, feature collectible bobblehead-like drawings of subjects, under titles like “Who Was Sally Ride?” and “Who Was Nelson Mandela?” The books’ popularity has launched spinoff series, including “What Was…?” and “Where Is…?”  Lauri Hornik, president and publisher of Dial Books, and the editor of the “Ordinary People” series, said the imprint plans to publish three new biographies by Mr. Meltzer each year—indefinitely. “We expected a gradual build, but there really has been instant interest,” she said. “I hope [we do] 100.”
Thriller writer Brad Meltzer, famed for such page-turners as “The Inner Circle,” is also writing children’s biographies of Helen Keller, Lucille Ball and others.