For Hamline creative writing Professor Sheila O’Connor, the month of April is sure to bring more than just showers. Her third children’s book, “Until Tomorrow, Mr. Marsworth,” is due Apr. 3. Set during the Vietnam War era, the novel tells the tale of an unlikely friendship between an 11-year-old paper carrier and her elderly neighbor.

“I began the new novel with the voice of the main character, the protagonist Reenie Kelly, and in the process I discovered a friendship that she had, or wished to have, with a reclusive pacifist named Mr. Marsworth,” O’Connor said, explaining her inspiration.

Instead of chapters, the story takes the form of letters.

“I’ve always been interested in the epistolary form, and as a writer I’m always looking for a new formal challenge, so that was part of what excited me about this book as well.”

O’Connor described the book’s evolution through a grand revision process.

“I wrote one draft, start to finish, that looks nothing like this book. Nothing. Different plot line and everything, but same characters,” O’Connor said. “And then I went away to an artist residency in Key West, Florida, for a month, and I just sat down and started it again, this time as an epistolary novel. The book from there went through many substantive revisions as I got closer and closer to what I wanted it to be about.”

O’Connor rarely bases characters directly on people from her own life, although every character has characteristics of people she has known.

“[At] the time period of the book, 1968, I was the main character’s age… I know what the world looked like to a child in a small town in Minnesota, that summer,” O’Connor said. “I like to have a cast of characters. I hope that each character brings a level of complexity, of humanity, and that within each character, the reader is called to understand something about being human that they didn’t quite understand before.”

While writing “Until Tomorrow, Mr. Marsworth” O’Connor’s most prominent influence was Bernard Edelman’s book “Dear America: Letters Home from Vietnam.”

She is specifically drawn to historical settings- her first children’s novel, “Sparrow Road,” is set in the late 1980s, while her second, “Keeping Safe the Stars,” takes place at the time of President Nixon’s resignation.

O’Connor has also written two books for adults: “Where No Gods Came” and “Tokens of Grace.” Despite their intention for an older audience, both feature young protagonists as well.

“The lives of young people are of particular interest to me, particularly young people who who are at risk in some way,” O’Connor said. “This may have come from the many years I spent working as a writer-in-residence in the schools, teaching poetry… because I heard so many of their stories and I recognized how monumental their struggles were.”

Following the release of her third book, O’Connor will host two publication launch readings, the first on April 7 at 2 p.m. at Wild Rumpus, and the second on April 15 at 3 p.m. at Red Balloon Bookshop.