The Father Brown mysteries are unique, I believe, in the genre of Mystery fiction. Father Brown is an unlikely detective, excessively ordinary and stupid looking. His extraordinary abilities lie in his careful knowledge of human nature, which his position as a priest and confessor gives him. He is also exceedingly rational in nature, but kind and humble and not at all caught up in his own abilities. The stories are interesting, ranging from the innocent and amusing, such as 'The Disappearance of Mr. Glass' and darker stories such as 'The Salad of Colonel Cray,' one of my favorites.
Published before WWI, the Catholic Chesterton points out some of the foibles and inconsistencies of the secular society in which he lives. Father Brown is very accessible and a joy to read, leaving the reader with a satisfied feeling and a smile.
I first read the Father Brown stories when I was 12, and had just finished reading my dad's copy of 'The Complete Sherlock Holmes' to death. He bravely gave me 'The Complete Stories of Father Brown', and I was hooked. Father Brown is one of my favorite detectives, not because he is witty like Lord Peter or brilliant as Sherlock Holmes, but because he is familiar and ordinary, and yet wonderful. The first story in the collection, 'The Blue Cross' is where we first meet Flambeau, the greatest burglar the world has ever known. He will turn up in more stories later on, but this is my favorite. Chesterton shows his own sensibilities and concerns with the way his pre-WWI society was going (spiritualism, excessive interest in the occult and eastern religions) in 'The Wrong Shape' which is a brilliant crime, and possibly one of the best-crafted mysteries of the Father Brown stories. Anyone feeling intimidated by Hercule Poirot or Sherlock Holmes or other classic detectives, or even just someone who is looking for something extraordinary to read, will enjoy Father Brown. His appeal is that he is so exceedingly ordinary and average in appearance and almost every other way, but he still finds himself in unusual and challenging situations, and uses his 'uncanny insight into human evil' to rescue innocents and solve mysteries.