As the hours tick down to Saturday's stroke-of-midnight release of the latest Harry Potter book, some parents are concerned that the kids lining up outside bookstores will be faced with a story as black as night itself.

"It's scary for younger kids, when you have animals turning into people and people into birds and things like that," said Geneseo, Ill., parent Marian Shannon. "It's maybe not for kids who are less than 8."

As Potter readers well know, the boy wizard's godfather, Sirius Black, has been killed right in front of him, he has cast the forbidden "Cruciatus Curse" on a witch in an effort to make her writhe in unspeakable agony and he has been prophesied to either kill or be killed by the evil lord Voldemort.

With the 12:01 a.m. Saturday release of "Harry Potter and the Half-Blood Prince" (search), the second-to-last book in the series, expectations are for the series to grow blacker still.

"It's been getting progressively darker throughout the series," said Ilene Cooper, children's books editor at Booklist (search) magazine. "J.K. Rowling (search) herself has intimated that she isn't sure Harry is going to survive the series. That's about as dark as you can get."

Some parents complained that the last Potter film, "Harry Potter and the Prisoner of Azkaban" (search) — which introduced audiences to the black-cloaked, soul-sucking floating "dementors" — was far too dark and horrifying for young children to see.

"When my family went, it was surprising to see how many parents brought 6-, 7- or 8-year-olds, and I was thinking, 'That's not the age group that this is for,'" said Wauconda, Ill., mother Colleen Kersting.

"One child screamed out in the theater and had to leave. I think parents were shocked at how violent and scary the movies have gotten," she continued.

Jennifer Brown, children's reviews editor at Publishers Weekly (search), said the darkening books should not come as a surprise.

"Rowling made clear from the very beginning that Harry would grow up from his first year at Hogwarts," the school at which children study how to become wizards in the series, said Brown. "Harry's parents are dead from the beginning."

However, she added, "the dementors in the third book were dark. Just the idea of a creature that can suck the happiness right out of you is pretty terrifying."

Even the pope has taken a swipe at Harry.

In a March 2003 letter to Gabriele Kuby, author of the German book "Harry Potter — Good or Evil," Benedict XVI, then Cardinal Joseph Ratzinger, expressed concern that the books "erode Christianity in the soul" of young people, Kuby said Thursday.

"It is good that you are throwing light on Harry Potter, because these are subtle seductions that work imperceptibly, and because of that deeply, and erode Christianity in the soul before it can even grow properly," Benedict's letter says.

But most parents say the latest books and films are OK for young audiences, as long as kids are able to understand that it is all make-believe.

"I don't think it's really, really dark. It always ends up with Harry offering some kind of hope and things turn out positively in the end," Greensboro, N.C., mother Mary McGinley said. "I think most kids understand that it's completely fantasy-based."

That said, the growth of adult interest in the books seems to support the idea that the series has gone beyond the genre of children's books.

More than a quarter of a million adults are predicted to purchase "Half-Blood Prince" on its first day of release in Britain, which would put the novel up with the hardback sales of all the heavy hitters in adult fiction there.

"It's really a phenomenon that spans age groups — it's taken on a life of its own," Cooper said. "As Harry has gotten older, the audience has gotten older as well."

Young readers who have grown up with the books seem to agree that as the story grows more dismal, it only gets better.

FOXNews.com interviewed the graduating 8th-grade class at Discovery Middle School in Alexandria, Minn., about the dark turn the Potter stories seem to have taken.

"I do think they have gotten darker. I think it has made the books marvelous! That's what a lot of people like to read about — kind of suspenseful and scary at the same time," said Discovery student Kelsey Olson. "I think it has had a great effect on the books and I hope they keep getting darker as the series goes on."

Sales figures back Kelsey up: Each successive Harry Potter book has done better than the last, and this latest installment is expected to equal, if not top, the whopping sales of Rowling's last book — "Harry Potter and the Order of the Phoenix," which sold more than 12 million copies.

Indeed, the majority of the 8th-graders who spoke to FOX News seemed to think that parents should butt out and let their kids have some fun.

"Snobby parents!" said student Alex Haugland. "The movies may be violent, but really, it's not that bad."

Cooper added that with fairy tales as old as "Cinderella" telling kids about evil step-sisters cutting their toes off to fit into a pair of shoes and having their eyes poked out by birds, children's capacity to absorb and appreciate dark material shouldn't be underestimated.

"Kids of younger ages read up," she said. "I would be surprised if she [Rowling] changed anything because younger kids were reading."