To the McGonagles, Harry was part of the family

The McGonagles are gifted readers, but sometimes they struggle with basic math -- like calculating the number of times that their family of five has read the six Harry Potter books.

Actually, that math isn't basic. The elder daughters and their mother have breezed through the series three times, maybe four. Maggie, 13, has read each book once. Every female McGonagle has listened to every Potter book-on-tape at least once, some twice, a couple thrice. Even Dad -- by far the least fanatical Potter reader in the family -- has heard a few books read aloud over the years.

The final count --drum roll! -- a McGonagle has read or been read a Potter book more than 100 times.

That's roughly one book per month since the series began in 1997. (And you don't even want to ask how many times they've watched the movies.)

So, for this Hingham family, the release of Book 7, "Harry Potter and the Deathly Hallows," on Saturday will mark a bittersweet final chapter in their love affair with J.K. Rowling's stories. "It's going to be upsetting," says Maura, 18. "There will be tears."

But first there will be page-turning. The McGonagles plan to purchase three copies of the final book -- one per daughter -- and bunker down in separate quarters until they all reach the last word (Rowling says it's "scar").

"They'll read the book straight through," says their mother, Kathleen. "Nonstop."

"I'm glad they're releasing it on a weekend," says Meghan, 22. "I was worried about having to call in sick to work during the week."

The first daughter to finish the book is supposed to pass her copy to Mom. Unless she decides to immediately reread it. "We don't share well," Meghan jokes.

The McGonagles began reading the books shortly after first print, and Harry soon became an adored sixth member of the family. On a 20-hour car trip to Chicago and back, the family listed in rapt silence to "Harry Potter and the Goblet of Fire" on audiotape. They named their collie mix after the character Sirius Black. In their basement, Kathleen keeps Potter memorabilia: a 1999 Time magazine cover story, instructions for Potter parties, and a photograph of 11-year-old Maura, in wizard hat, with Rowling.

"The stories have aged with the readers," Meghan says. That's one reason the family has remained devoted to Potter for so many years, she says. Also, Kathleen adds, the books offer new clues with each reading. "The first reading is so frantic," she says. "You just want to know what's going to happen. The second or third time is less frantic. Each time you pick up something new."

On Friday, as the clock nears midnight, the McGonagles will host a Potter trivia session at Buttonwood Books and Toys in Cohasset. Kathleen may dress as Minerva McGonagall, a Potter character with a last name similar to the family's. Then they will begin reading -- racing, really -- to Page 784.

But even after they finish "The Deathly Hallows," Kathleen says, the McGonagles will remain, in essence, Potters. "The books are like good friends," she says. "They will definitely be reread, or listened to again."

Plus, Maggie says, "There will be the movies."

Robbie Brown can be reached at jbrown@globe.com.