There's a reason that tissue packets are sometimes handed out at author John Grogan's book signings. His "Marley & Me: Life and Love with the World's Worst Dog" (William Morrow, $21.95) may very well be the feel-good book of the year. It's definitely the dog lover's book of the year.

Word of mouth and glowing reviews have propelled the sentimental memoir onto the best-seller lists since its publication in mid-October, with 550,000 copies in print.

No one is more surprised by all the attention than Grogan. "I had zero strategy about how this would play in the marketplace. It really was one of those stories told from the heart."

In 1991, Grogan and his wife, Jenny, adopted a labrador retriever puppy and named him Marley after the reggae star. Like dog owners everywhere, they marveled at the trouble Marley could get into, especially the things he could eat: stereo speakers, dirty diapers, couch cushions, drywall, shoes, towels, even a home pregnancy test strip.

As the years passed, Marley's antics became the stuff of legend in the family. And after Marley's death in December 2003, Grogan, a columnist for The Philadelphia Inquirer, wrote a tribute to his beloved pet.

"I wanted to write a column about how woefully bad he was in some respects, but also about the great joy he brought our family," he says. "All the humor and laughter, and in a bigger sense, some of the lessons about love and loyalty that we actually took from this big, dumb, loopy dog."

Reader response included condolences from more than 800 dog lovers. It was then that Grogan decided to fulfill a dream he'd had for years: to write a book about Marley.

"I don't consider myself one of these nutty dog people who writes these saccharine things about animals," says Grogan, 48, who lives near Emmaus, Pa., with his wife and their children, Patrick, 13, Connor, 12, and Colleen, 8. "It was the bigger story, the story of our family, the dog, the growth and the gradual melding of all these disparate units into one cohesive thing called a family."