Brian Browning from Perton had returned home after a spell in New Cross Hospital and was surprised to find his novel Secrets, was on sale on Amazon and had already earned him more than £1,000 in royalties.
The 84-year-old had written the romance 10 years ago after retiring, but had lost it on his computer.
However, he had kept a hard copy, which he lent to his grandson Samuel Leeds to read, with Samuel and his wife Amanda working to write up the story and get it published.
Brian said he was gobsmacked to find his grandson had got the book published and then presented him with the amount he had earned from the sale of the printed edition and Kindle version.
He said: "I was just dumbfounded when he told me I’d sold more than 1,000 copies. It’s like Christmas coming.
"It’s always been my dream to have a book published and I’m so thrilled.
"It’s the best gift he could have given me. I can’t thank him enough."
Based on real events, Secrets spans three decades, beginning with the Second World War, and tells the story of a mother and daughter who discover how cruel love can be.
A web of secrets is slowly revealed as lives are unravelled in the knife-edge world of war and the ensuing years.
The 388-page novel also focuses on one family’s struggle to regain normality after the war years, as well as exploring the rise and decline in British manufacturing and the obstacles facing women in the work environment.
Secrets is available on Amazon at £12 for the paperback or £1.99 on Kindle.