In publishing, all dogs go to heaven, but what about cats, horses and birds?

Ever since author John Grogan scored a megahit with 2005’s Marley & Me, publishers of all stripes have been looking for the next chart-topping, boo-hooing, man-and-his-dog story.

Nowhere has this been more true than in religion publishing, where books such as Heavenly Humor for the Dog Lover’s Soul,  The Dog That Talked to God and Four Paws From Heaven have been good sellers for their various Christian publishers. These books look beyond the earthly relationships between people and their pets to the religious and spiritual lessons the four-footed can teach.

But a decade is a long time for a trend, and as religion publishers prepare for this year’s BookExpo America, where booksellers look ahead to Christmas, they are adding cats, horses and even birds to the animal spirituality roster.

“These books are about life and relationships, and that draws people in,” said Sheila Waldman, “president of relationships” at tiny Tristan Publishing, which is bringing My Boy, Ben: A Story of Love, Loss and Grace by tennis pro David Wheaton, about his yellow labrador, to Book Expo. “They are timeless and universal.”

They are also potentially big money-makers. Americans spend more than $60 billion on their pets annually, according to the U.S Department of Labor. That’s a number any publisher ― religious or otherwise ― would lie down and roll over for.

“As a business, it just makes sense to publish books with great stories about people connecting with animals,” said Kim Moore, senior editor at Harvest House, an evangelical Christian publisher whose 2006 release Four Paws from Heaven sold 125,000 copies ― a big number for a small publisher.

At New York's BookExpo, Harvest House will move beyond paws to hooves with Great Horse Stories: Humor and Wisdom from Our Majestic Friends by Rebecca E. Ondov, about horses who help people. Moore said animals are a perfect subject for religion houses.

“The Bible says God is loving towards all he made and there is something about connecting with God when you care for your pets in the way he cares for us,” she said. “It gives us a glimpse into who God is and how we can relate to him.”

Lynn Garrett, senior religion editor for Publishers Weekly, a trade magazine, said books about animals and their humans have been a publishing mainstay since the 1960s’ Travels with Charley by John Steinbeck. “Now we are seeing them in the religion category because, I think, there definitely can be a spiritual aspect to our relationships with animals,” she said.

As for the shift beyond dogs, “that makes sense, since there are successful programs using horses for therapy ― for vets with PTSD, for disabled kids and prisoners,” she said. “That’s just another animal people can have a spiritual bond with.”

That’s been the experience at Revell, a division of Baker Publishing Group, which will bring The Cat on My Lap: Stories of the Cats We Love by Callie Smith Grant to BookExpo. Grant is the pen name of Revell executive editor Lonnie Hull DuPont, who has been writing spiritually inspiring animal books since 2007.

“There was resistance in the market for a while” to religion titles involving animals, she said. “But now people don’t feel silly to admit they love their animals and are grateful for them.”

She expects to see more religion books on working animals, perhaps cancer-sniffing dogs or therapy horses, and said even birds are not out of the question. “They are not cozy or furry and we can’t ride them, but the Bible is full of them.”