I just finished reading William Oddie's biography of Chesterton, and it is fantastic. Taken together with Joseph Pearce's book, Maisie Ward's book, and if you want to be totally well rounded, several others (Ada Chesterton's, Father O'Connors, Michael Ffinch's, Clemens's, etc.) it provides a new and wider-ranging view of the spiritual development of Chesterton's, well, spirit. The reason it is wider ranging is because Oddie had access to more papers and notebooks than previous biographers.
The subtitle is "The Making of GKC 1874-1908", and that covers birth through Orthodoxy's publication, and, as Oddie states near the end, Chesterton's spiritual growth peaked with Orthodoxy and he never strayed after that in any other directions.
I'm going to be discussing the book here, and on the podcast, because there were so many insights worth talking about and thinking about, my mind is just happily processing it all.