Rob Delany's A Heart That Works explores the loss of his child, and has pushed the comedy actor to become a voice for bereaved parents.
In 2022, Delaney detailed the loss of his son Henry in his memoir, after revealing his son had died at the age of two and a half in 2018.
This year, Delaney was also part of the Edinburgh International Book Festival where he discussed grief at the loss of his son.
How did Rob Delaney's son die?
In his book, Delaney revealed Henry died after being diagnosed with a brain tumour. The Catastrophe star revealed how he learnt of his son's diagnosis the day after winning a BAFTA Award for said film.
An extract from his book published in the Sunday Times provided a recount of the difficult period for him and his wife Leah after Henry's tragic death.
"Grief drove a bus through the part of my brain where memories are stored," he said. "After the MRI, Dr Anson confirmed that Henry had a large tumour in the back of his head, near his brain stem.
"He delivered the news calmly, and ended by saying a paediatric brain surgeon would come to see us within a few hours. We sank inside ourselves."
He explains how they were introduced to a brain surgeon at Great Ormond Street Hospital who would try to surgically remove the tumour just two weeks after Henry had turned one.
After two months in the intensive care unit, Henry was moved to the cancer ward where he received chemotherapy for several months.
When Delaney learnt that Henry's cancer had started to return, he said his "stomach filled with stones" as he and Leah understood there could be no more treatment.
Henry was then given just three to six months to live and tragically passed away in January 2018.
Why did Rob Delaney write A Heart That Works?
During an appearance on Wednesday's (6 September) Loose Women, the 46- year-old spoke about his book, and how it helped him process his grief. He said: "I'm glad I wrote it. It felt good to organise my thoughts and feelings in a formal manner.
"And realising how wonderful my wife and Henry's brothers were, it made me fall more in love with my family.
"The fact it's out there feels really good, other bereaved parents can feel recognised.
"The response has been staggering and unbelievable but my ego is very right-sized by this whole thing. My story is no more or less important than anyone else's.
"Our son died and if we talk about it openly and honestly we can help other people through it."
His book also sees Delaney explore other emotions as he goes into detail about the "tremendous anger" he felt as he processed the loss of his son, admitting he would fantasise about smashing car windshields.
He said: "Yes there's anger in the book but there should be - my beautiful little boy died. I knew there could be hope in the book, I could show it but couldn't tell it."
Cancer in children
According to Cancer Research UK, around 1,900 children (aged 0 - 14 years) get diagnosed with cancer each year. This number includes non-cancerous (benign) brain tumours. Children develop different types of cancers than adults but they often have the same types of treatments.
Cancer in children is rare, but out of the many different types of cancer, the most common types in childhood are:
cancers of the brain and spinal cord
Other types of children's cancers include:
lymphoma (cancer that starts in the lymphatic system)
muscle or bone cancers, such as rhabdomyosarcoma, osteosarcoma, and Ewing's sarcoma. Rhabdomyosarcoma is most common type diagnosed in children.
neuroblastoma (a cancer of nerve cells)
Wilms' tumours (a type of kidney cancer)
retinoblastoma (a type of eye cancer)
More than 80 out of every 100 children (80%) diagnosed with cancer will live for at least 5 years or more and most of these children will be cured. Hodgkin lymphoma and an eye cancer called retinoblastoma are curable in more than 95 out of 100 children (95%).
Even though cancer is not common in children, it is the leading cause of death from illness in children between the ages of 1 and 15 - the second most common cause is accidents.