Robin Roberts with her Jack Russell terrier. (Robin Layton)

A book by photographer Robin Layton will showcase dozens of dog owners' heartfelt letters to their pets along with photographs. Celebrities such as Kristin Chenoweth and Kathy Najimy are featured in " A Letter to My Dog," as are ABC News' own "Good Morning America" co-anchor Robin Roberts and "Nightline" co-anchor Cynthia McFadden. The book will be published this fall by Chronicle Books.

Layton, who runs a blog of the same name, also selected a letter from Lt. Chet Frith. Frith, an Iraq war veteran, said that he felt like his "world was falling apart" after he returned home from combat.

"I desperately needed help. And then you arrived and gave me hope," wrote Frith, who is married with two children. "You have my back everywhere we go and make me feel safe in places I once avoided. You remind me every day that there is good in this world and there is love. You show me how to forgive and forget and help me relax in times of stress. Most importantly, you bring a ray of sunshine to my family and me."

Chet Frith and Gunner (Robin Layton)

Layton said working on the book has been "a pure joy."

"Every time an owner walks into the room with a dog, their face just lights up and that to me is the best to witness because (a) dog's love is so unconditional and so pure," she said. "If you had a bad day, if you're down, if you're a celebrity or whatever, your dog is just going to love you unconditionally and that's just amazing to see."

A portion of the proceeds from the sale of the book will benefit The Humane Society of The United States.

See more about the bonds between dog owners and their pets tonight on "Pet Crazy" on " 20/20" at 10 p.m. ET.

Robin Layton with her dogs Bella and Monkey. (E. Shakti Chen)