Jeni Stepanek has gone through what no mother should: she lost her 14-year-old son, Mattie, after his lifelong struggle with a rare form of muscular dystrophy. Now she’s come out with a new book, Messenger: The Legacy of Mattie J.T. Stepanek and Heartsongs, to pay tribute to the boy who inspired the world with his poems of hope and strength.

“Mattie’s body passed away five years ago, but I wrote this book because Mattie’s life is not about loss,” Jeni said on Good Morning America. “His life is a celebration of wit and wisdom and hope and peace, and his legacy’s getting bigger every year. And it was time to share the true story of his life.” Check out the video on GMA’s website.

Jeni, who is confined to a chair and must use a breathing tube, says it was challenging raising her children after being diagnosed with the disease — and realizing she had passed it onto all of them. Still, she kept the faith — and was constantly inspired by Mattie. Jeni said that from the age of 3 to 4, Mattie had said that his “purpose for being on earth was to be a messenger, to make people smile despite challenges.”

Messenger is “going to make you laugh,” she said. “It will make you cry in a few places…but people need to understand that Mattie was an ordinary child who made extraordinary choices. Mattie’s message is alive and each of us can choose to be a messenger.”