These stories are worth reading as "classic" detective fiction, however the concept of a super intelligent sleuth who solves the mystery solely on the basis of his superior intellect (no matter how unassuming the package) seems very dated now.
I think Chesterton meant these stories to serve as social commentary and unobtrusive evangelism. My favorite of the collection is "The Queer Feet." In this story Father Brown solves a theft at which takes place at a hotel "which paid not by attracting people but actually by turning people away." It concerns a club for wealthy men whose very purpose is purposelessness. The club holds dinners filled with intentionally meaningless rituals at a hotel that is popular with the rich and powerful precisely because it is inconvenient: "The society had a vast number of ceremonies and observances, but had no history and no object; that was where it was so very aristocratic."

The story itself isn't even remotely plausible but Chesterton has a field day describing the club, its rituals, and the hotel. The story is genuinely funny and could have been written yesterday, though today's club president would be Kanye West rather than the Duke of Chester.