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What: “Last Days of Summer,” by Steve Kluger

Publisher: Avon Books, Inc. (353 pages)

Price: $21

Baseball, war and growing up.

These three themes are intertwined in “Last Days of Summer,” a novel that tells the story of a boy growing up without a father in 1940s Brooklyn.

Through letters and newspaper clippings, we learn about an unlikely friendship between a baseball player and a boy who idolizes him, a relationship that develops into a bond as strong as any father and son could have.

What makes this story great is the way Kluger takes two people who need to grow up and lets them mature with each other’s help over two years.

A 19-year-old star with the New York Giants, Charlie Banks cares only about himself.

By the time he’s a 21-year-old headed off to World War II, Banks leaves behind a wife he loves and a boy he cares for like a son.

At the same time, Joey Margolis goes from a foul-mouthed 12-year-old lacking discipline and guidance to a young man hobnobbing with celebrities.

And the whole time, their bond is baseball.

A fan of the player while Banks was in the minors, Margolis begins pestering the slugger with letters to his house. Smarter than most adults, Margolis is able to follow Banks through the mail even as he changes his address to avoid the youngster.

Through persistence, Margolis [who even writes political suggestions to the White House and gets personal responses from Franklin Roosevelt’s press secretary] persuades Banks to visit him. Over the two years, they grow from buddies to best friends and finally almost to father and son.

Their relationship receives its greatest strain when Banks is sent off to war.

“Last Days of Summer” isn’t about baseball. It’s about a boy struggling to grow up without a father and a young man’s acceptance of that role.

This is a story worth reading.