But his son's decision to join the Marine Corps in 1999 and the resulting emotional journey for his family led the Salisbury screenwriter-turned-fiction novelist into completely new territory.

Schaeffer's experiences with a son in the military were pivotal to his role as both a father and novelist.

"When your son puts on a uniform and goes out and defends you, regardless of your politics," he said, "it's a humbling experience."

Schaeffer and his son, Cpl. John Schaeffer, shared their letters back and forth during boot camp and beyond in the 2002 book, "Keeping Faith: A Father-Son Story About Love and the United States Marine Corps."

Schaeffer followed up with a glimpse into his own private journal in "Faith of Our Sons: A Father's Wartime Diary," and then "Voices From the Front - Letters Home from America's Military Family," a collection of hundreds of personal, often emotional letters to and from servicemen and women in Iraq and Afghanistan following Sept. 11, 2001.

He also co-authored "AWOL: The Unexcused Absence of America's Upper Classes from Military Service - And How It Hurts Our Country" with former Clinton White House aide Kathy Roth-Douquet.

Now, Schaeffer has returned to the fiction realm. But the military and the author's own inner struggles with the current tenor of society remain at the forefront.

In "Baby Jack," which is due out Oct. 1, Schaeffer delves into the worst-case scenario for the parent of a child in the military. It tells the story of a young Marine's path from recruitment to death, and his family's attempts to cope with and understand his heroism and sacrifice.

Calling it "a modern novel with a social conscience," Schaeffer said the book is also a metaphor for the larger issue of the class division between the people who typically serve in today's military and the generally wealthier and more educated individuals who do not enlist.

"There's a part of America who does not come to terms with service or sacrifice anymore," he said."

Set in Newburyport, Salisbury and the surrounding region, "Baby Jack" is told in the voices of youngest son Pfc. Jack Rutherford Ogden, who is killed soon after being deployed to Iraq, and his father, mother, sister and girlfriend who are left behind to grieve.

Patriarch Todd Ogden, a successful painter, grew up in the baby-boomer era of make love, not war. His life of privilege and upper-class outlook doesn't mix with his son's desire to enlist. Jack's Wellesley-bred mother thinks her son has "better options" than the military. The only one who seems to truly understand Jack is his girlfriend.

Jack's family bears many similarities to Schaeffer's.

"This book is very close to the bone," said Schaeffer, who has lived on Ring's Island on the banks of the Merrimack River for 27 years with his wife, Genie. "It was very tough to write."

"Baby Jack" is also the story of Newburyport since its redevelopment into what Schaeffer says is an upscale, gentrified community. Schaeffer uses the class differences that exist between Newburyport and Salisbury as a microcosm for what he sees occurring in the country.

"It's the story of the Americans who don't serve in the military anymore," he said. "We're living in two separate worlds separated by money, class and education."

Schaeffer said there was a time in the mid-1950s when half the graduating class of Ivy League schools served in the military. Today, that number is down to less than one-half percent. While not necessarily a supporter of a draft, Schaeffer is a proponent of universal service that would see young adults volunteering between high school and college.

Despite his strong opinions, Schaeffer says his book is far from political.

"My views are not conservative or liberal, Republican or Democrat. This is not about politics, George Bush or the Iraq War. It could be set in any war," he said. "It's about the virtue and sacrifice and the redemption that is found in serving others."

After two tours in Afghanistan and another in Iraq, Schaeffer's son finished up his service in the military a few years ago and is studying modern European history in college. But the letters and e-mails from members of the military and their families that started arriving after "Keeping Faith" was published continue to come by the hundreds each week.

They talk about boot camp, about combat, about hope and courage, and loss and grief. Schaeffer makes sure to answer each one of them.

"This is something that cuts people right to the heart," he said.

"Baby Jack"

By Frank Schaeffer

Carroll & Graf, Oct. 1

320 pages

$24.95

If you go

What: Reading and book-signing

When: Thursday, Oct. 12 at 7 p.m.

Where: Jabberwocky Bookshop, The Tannery, 50 Water St., Newburyport.

How: Free. Call 978-465-9359 or visit http://jabberwocky.booksense.com for more.