If you are interested in Chesterton as a complete writer, I would recommend starting with Ignatius Press’ essay collection, “In Defense of Sanity.” It will give you a good sense of Chesterton’s range as a writer.
If you just want to dive into his strictly apologetic work, “Orthodoxy” is where you want to start. “The Everlasting Man,” as others have noted, is considered his
magnum opus, but you’d do better to save that until you’ve gotten a feel for his style, which is notoriously paradoxical, and never moreso than in “The Everlasting Man.”
As far as his fiction goes, “The Ball and the Cross,” is probably his most accessible and philosophically profound work. You’ll know by the end of the first chapter whether you’re hooked or not. Alternatively, “The Man Who Was Thursday,” is probably his most famous novel, though it is a bit more cryptic and less explicit in its message than “The Ball and the Cross.” Both contain heavy doses of surrealism.
Finally, one can never forget his wonderful “Father Brown” short stories, which are some of the finest specimens of detective fiction ever penned.
In all reality, it’s hard to pick a “best work” from Chesterton, because his writing was consistently profound and dauntingly prolific. In the 35 or so years of his literary career, he penned over 100 books, 5,000 essays and hundreds of short stories. But none of the suggestions that have been made here would be a bad place to start.
