First off, let me say that Nicholas Shakespeare's biography will ever be the standard work on Chatwin. Like many others I think his book is one of the great biographies.
This is not to dismiss Susannah Clapp's book at all, for this is a different kind of book. Its introduction, in which she tries to capture the allure of Chatwin, is excellent. Where this really book really scores, however, is in the unmatchable insight Clapp, as Chatwin's editor, can bring to bear on his methods of composition and revision. Again, this is something covered well by Shakespeare on a book-by-book basis in his biography. Clapp, however, is able to reveal exactly the nature of the collaboration between her and Chatwin. True to the title this is a portrait of a working writer, and, great and distinctive as his books are, it turns out none of them appeared fully formed, and took a lot of paring down and shaping.
I'm still somewhat in awe of him as a creative artist, but after reading her blow by blow accounts of how a book like "In Patagonia" was honed at the editing stage, it's good to know he was mortal after all. Chatwin was many things, but one thing that's overlooked is that he was willing to do a lot of hard graft. Something else is also for sure: If it wasn't for the people around him who believed in him and nurtured him, it's doubtful he would have had the impact he had and continues to have.