Enter the Saint (1931) was Leslie Charteris' second foray into the Saint universe, but he liked it so much better than the book in which our hero first appeared, that he liked to think of it as the start of the series (which eventually grew into dozens of books, movies, TV shows, and a 1997 film I never heard of starring Val Kilmer).
And it is easy to see why the character was so popular -- known as "the Robin Hood of Modern Crime," Simon Templar, aka The Saint, is a moral criminal who steals from immoral criminals and donates all their ill-gotten wealth to charity, minus a 10% collector's fee for him and his compatriots. He is stylish, witty, smart, and very good at driving fast cars in a dare-devil fashion through the countryside. He calls everyone baby, sweetheart, angel, or love. He is just and moral and righteous, but he also drinks a lot, has a sexy and smart girlfriend, and knows how to crack a joke.
In this book, Charteris gives us three novellas staring The Saint and his gang as they outwit criminals and simultaneously help and avoid the great Inspector Teal of Scotland Yard. I get the feeling that the same thing happens in all the other books too, but I can't imagine getting tired of it. I'd never read any Leslie Charteris before, but I'd love to read more. And make sure to check out his Wikipedia page -- his biography is almost as exciting as his books.
[Super exciting back cover available here!]