I read this book in two days. It is only the second Chesterton novel I have read after the celebrated "The Man Who Was Thursday". As has been noted elsewhere, this novel is rife with Chesterton's personal philosophy of joy and astonishment at the universe and the character of Innocent Smith could very indeed be Chesterton himself.
Anything by Chesterton is worth reading and, while I never realized what an exceptional writer he was at painting a portrait with words, I feel that the novel was lacking due to the excessive amount of plot tied in to the court case and the corresponding letters attached to the trial. I would have preferred Chesterton expand the first part of the book where Smith's innocence and whimsy profoundly affects the denizens of Beacon House (a particularly enjoyable part was when Smith proposes that women could be more economical and stylish by using chalk to constantly draw new designs onto a dress only to dust the colours off once they were tired of them). Because much of the novel has to do with a court case and letters, many of the characters are left undeveloped and underutilized, especially those not participating in the trial such as the female characters.
The ending involving Dr. Warner is simply baffling.