Molly Shannon Writes Memoir About Life After Mom and Sister's Death: 'It Gives Me Gratitude'

"I felt like I had been through a war," says Molly Shannon, reflecting on the tragic accident that altered the course of her life forever.

When the award-winning actress was 4 years old, her mother, little sister and cousin died in a car crash. Her grieving father, who had been driving while under the influence, was badly injured. He had to relearn how to walk — and raise Shannon and her sister all on his own.

"For show biz, if I did interviews, I felt like, 'Oh, don't get too dark with this talk show host,'" Shannon — known for her portrayal of eccentric characters like Mary Katherine Gallagher on Saturday Night Live — tells PEOPLE. "But sometimes I can be deadly serious."

After years of planning and dreaming of writing a memoir, Shannon, 56, is finally opening up about the pain and grief of her past — as well as the humor and healing she's found since. Her book, Hello, Molly!, will be published by Ecco on April 12, 2022, she shares exclusively with PEOPLE.

The memoir explores Shannon's complicated and deep connection with her father, her journey as an actress and comedian and a behind-the-scenes look at her favorite memories from SNL. The result is "hilarious and heartbreaking," according to the press release.

"The book is a testament to my family," Shannon says. "It's the good, the hard — everything we've been through. I hope that it adds up to being a lovely portrait."

Since she was in her 20s, Shannon has been jotting down notes and memories, which she then referenced when she began writing Hello, Molly! a couple of years ago.

"I definitely always wanted to write about my dad," she says. "He was such a big character in my childhood, so I would always take notes of funny things that he said or how he spoke. Always. He was just such a big influence on me and my characters on SNL."

More than anything, Shannon wants to her memoir to reflect her "deep love" for her father, in all of his complexity. Together, they navigated a devastating situation and found healing. She also wants to give people struggling with adversity "hope to persevere."

"My dad was always very open [about the accident], but I think when stuff like that happens, it's like letting the water settle," says Shannon of dealing with her grief and confusion after the death of her three family members. "You throw a coin in water. You have to wait for it to stop rippling and let the water settle."

While there are difficult moments in the book, Shannon says she's processed most of them through therapy. "There were confused feelings, questions that needed to be answered," she says. "But I hope that there's a lot of forgiveness on the pages because that's how I feel. I love my dad and we were very close."

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With her father's support and encouragement, Shannon went on to win awards for her roles in shows like SNL, Will & Grace and Other People. She will soon reprise her role in the critically acclaimed comedy The Other Two. Part of the reason Shannon has fared so well in the tough world of show business is because of the "bounce-ability" she learned early on, she says.

"That kind of struggle at the beginning gave me a certain bounce-ability in show business," Shannon says. "It really gave me this ability to handle rejection because I've been through so much when I was little. I was like, 'Well, nothing can be as bad as that.'"

Shannon brings the same dauntlessness and energy to her writing.

"I like the quiet of a book. It's so different than performing," she says of the writing process. But she admits that she felt more "vulnerable" while writing her memoir than she has on set.

That feeling hasn't prevented her from sharing past pain in her book — or her gratitude for the life she's living.

Shannon says that losing her mother when she was so young changed her whole perspective. "I think any amount of time you have on earth with somebody is a good amount of time," she says.

"Every day of my life, I think, 'Oh my God. I'm alive. She never got to do this. I get to do it and I get to see my daughter apply to colleges this year,'" says Shannon, who shares daughter Stella and son Nolan with husband Fritz Chesnut, an artist.

"I'm seeing them as teenagers now and getting to be their mother and outlive what my mother was able to do," she continues. "It's profoundly healing, you know? It gives me gratitude."

Hello, Molly! will be published in April 2022.