"Gods and Generals" follows Confederate Gen. Thomas "Stonewall" Jackson through the early years of the Civil War and shows how civilians dealt with the war's carnage.
"Last Full Measure," the third book in the series, picks up after "Gettysburg" and traces the war to its conclusion.
Shaara, who kicks off a 35-city book tour on Thursday to promote "Last Full Measure," said scenes from both films will probably be shot next year.
With 10,000 re-enactors scheduled to descend on Washington County for the filming, he said it makes sense to get as much on film as possible.
"It's what would have happened if Mel Gibson had intended to film a 'Braveheart II,'" Shaara said.
When Shaara and Maxwell formed Antietam Filmworks last September, county leaders hailed it as a unique opportunity to bring a piece of the national spotlight to the area.
The county got a taste of that spotlight about a month ago when Maxwell cast actress Miro Sorvino in the role of Joan of Arc for his current film. Pam Gleason, who staffs the Hagerstown office of the film company, said Maxwell took Sorvino to a re-enactors ball at Antietam National Battlefield.
In trying to pay for the project, though, Maxwell and Shaara have shunned the traditional Hollywood route. They have sought and received $300,000 in loan guarantees from the county and city governments.
Shaara said several deep-pocketed investors who normally do not put up money for movies have expressed interest in investing in "Gods and Generals."
"This is not a Hollywood movie. This is, for lack of a better word, an American movie," he said.
"We're really at the beginning of the process. It's hard to know, even now, what the film will cost," Maxwell said.
Over the next several months, Shaara said crews will continue to seek potential filming locations. He said uncontrollable factors have ruined several promising sites.
One spot, for instance was perfect except that cars from a nearby highway could be heard, Shaara said. Another site was nixed because it would have cost too much to bury nearby power lines.