I myself recently returned to the Catholic church, and I really wanted to like Chesterton's book. And I did *enjoy* it. His style is entertaining, and as a long-time C. S. Lewis fan I now know where Lewis got his own style.
But in the end, what Chesterton seemed to have written was not Why I am a Christian or Why I am a Catholic, but Why I am a European. And he seems to have thought this amounted to the same thing.
His dismissal of Islam as being cruel and suited to people from dry places is astonishing. His dismissal of knowing God within as leading to....Tibet is likewise astonishing! A lot of his argument seems to be prejudice dressed up as reasons. That he likes romance and adventure, and finds Christianity romantic and adventurous is all very well, but if Christianity is true, it is intended for Tibet and the dry places of the earth as well as the cozy English countryside that he loves.