So if we should only read GKC, then we should not read Dale Ahlquist. But as my long suffering Wife got me the book for my Birthday, it would have seemed ungrateful not to read it. Also I don't just read GKC, there's Belloc, Tolkien, Pearce, Tolstoy, Shakespeare, Belloc, Cecil (GKC's brother) etc.
So, unless you're only going to read GK Chesterton, ignore Mr Ahlquist's advice and read his book.