Although most teens would jump at the chance for a road trip, sisters Octavia and Tali are less than thrilled at the prospect of spending their summer on the road. Why? They have to spend the summer with their crazy grandmother -- who insists they call her "Mare," not "Grandma."

Mare wears high heels, drives fast and seems to have nothing in common with Tali and Octavia. Although the girls think that the trip will be unbearable, they soon discover otherwise.

As the cross-country trip progresses, Mare tells Tali and Octavia about her life growing up poor in wartime Alabama. Mare, whose real name is Marey Lee Boylen, faced an uncaring mother and her abusive boyfriend, all while trying to take care of her little sister Josephine.

When Josephine gets a chance to get away and live with an aunt, Mare sees no reason to stay with her mother. She lies about her age to join the new all-black Women's Army Corps.

During her training with WAC, Mare learns about everything from gas masks to spotting enemy planes and discovers new strength and courage. Although she and her comrades face racial and gender discrimination, they prove that they are willing and able to work hard at their jobs for the good of their country.

As World War II progresses, Mare's unit is shipped to Scotland, then England, where they are given the task of sorting enormous amounts of mail for the men fighting in the European Theater. The WACs realize how important this task is as they see the effects of mail delivery on the soldiers' morale.

The book switches between Mare's story as a WAC and Octavia's view of their road trip. Tali and Octavia, usually at odds, learn to be friends, and the girls develop an understanding, even a friendship, with their grandmother. As Mare tells her story to her granddaughters, she is also teaching them about her and her comrades' experiences with discrimination, homosexuality and teenage pregnancy.

"Mare's War" offers a unique view of WWII while showing the similarities of teenage girls of different eras. Mare's struggles as a young black woman in the 1940s are not so different from the pressures of teenagers today.