The first episode featured British author and comedian David Walliams.
Ahern said the earliest books she read as a child, including her collection of Ladybird books, helped her learn how to tell a story.
Since releasing her debut novel in 2004, Ahern has sold 25 million copies of 19 novels worldwide.
Guests on Tubridy’s podcast are asked about their favourite childhood book. Ahern put forward The Enchanted Wood by Enid Blyton and said the book still influences her writing today.
“Even when I’m writing now, I think my character is pretty much climbing up the tree to see what world she is in and that is the basis of all of my stories: ‘What land is it now for my character?’ I think it began with this,” she said.
She credits her hugely successful debut novel PS I Love You with being the book that changed her life.
The New York Times Best Seller sold millions of copies and was adapted for the big screen in 2007, starring Hilary Swank and Gerard Butler.
“I was very fearful at the time and I needed the people around me so much. And I thought, ‘What if I lose them? What if I lost anybody?’
“And that was so terrifying, thinking of all the ways you could hold onto somebody,” Ahern said of the concept for PS I Love You,” she said.
“And then it became not me and it became a story, like ‘What if someone wrote letters?’ I love handwriting, I think if someone writes something in their writing it has got a bit of their soul and I keep it and treasure it.”
While studying for a master’s degree in 2002, Ahern, overcome with nerves over public speaking, decided to drop out after learning she would have to speak in front of the class.
She started writing PS I Love You that night when she arrived home, was encouraged by her mother to send the first chapters to an agent and secured a two-year book deal within weeks.
“When I signed the contract, it said word count 80,000 – 100,000 and I had no concept how big a book that was. So, I went out and I bought a book and I counted the number of words on the first page and multiplied that,” she said.
“Just to get an idea – and because I was so young and I didn’t want to look like I didn’t know what I was doing! And at the back of this [manuscript] – I also didn’t know what a word count was on a computer, had no idea – I counted all my words.”
Ahern and Tubridy also speak about the book that made her cry and Tubridy’s own weekly ‘Ryan Recommends’ segment of the podcast.
The second episode of The Bookshelf with Ryan Tubridy featuring author Cecelia Ahern is available now on Spotify, Apple Podcasts, other podcast platforms and YouTube.