A decade ago, I wrote the book "The Life You Can Save: Acting Now to End World Poverty." This month, a fully revised 10th anniversary edition was published, and is available, free, as an e-book and audio book.

The chapters of the audio book are read by celebrities, including Paul Simon, Kristen Bell, Stephen Fry, Natalia Vodianova, Shabana Azmi and Nicholas D'Agosto. Revising the book has led me to reflect on the impact it has had, while the research involved in updating it has made me focus on what has changed over the past 10 years.

The book argues that for middle-class people living in affluent countries, abiding by the traditional moral rules against lying, stealing, maiming or killing is not enough. Living ethically in today's interconnected world involves helping people who, through no fault of their own, are suffering in ways that we could easily prevent or alleviate.