John Stamos admits he "never planned to write" his forthcoming memoir "If You Would Have Told Me," until the death of his dear friend Bob Saget in January of this year.

"After losing Bob, finally becoming a father, and wanting to honor all the colorful people who have made me who I am today, I figured if not now, when?" Stamos wrote in the caption of an Instagram post on Wednesday, announcing the book.

He called the release, due out next fall, "my story about Hollywood, fame, fortune, and f***ups."

"It's also about home, heart, and healing," the "Full House" and "Big Shots" star wrote.

Publisher Henry Holt teased in the announcement, "'If You Would Have Told Me' is the story not only of a life lived in front of the camera, but of the surreal highs and devastating lows of a misunderstood heartthrob who has always remained a dorky kid from Orange County, and of his midlife quest to find sobriety and a family of his own."

Stamos called the writing process "cathartic and healing and sometimes heartbreaking."

"I hope my memoir offers a window into my heart and mind and helps readers find little moments of magic that make life worth living," he said.

"Honestly, while writing this book I've realized I have about a million stories to tell, and I think you may like at least four hundred of them," he added.

Saget, 65, was found dead in a hotel room in Orlando, Florida, on Jan. 9. In February, his family revealed he had died from head trauma.

"[Authorities] have concluded that he accidentally hit the back of his head on something, thought nothing of it and went to sleep," his family said in a statement at the time, obtained by ABC News. "No drugs or alcohol were involved."