Yes, I have actually read Gavin Menzies' 1421 - The Year China Discovered the World.
It was only a year ago, a time when I was wandering on the streets of London during the day and reading books at night. I picked it up cheaply in one of the many bookshops on charing cross road, and when I finished I gave it to one of my chinese flatmates whose name I never quite worked out.
It is a very readable book. Gavin writes well, he conveys the excitement and sense of adventure of those heady days, and his story-telling keeps us turning the pages. But then, the topic is so fascinating. European nations conquered the world on the strength of their ships and guns. But here was the Chinese naval fleet, far larger, better equipped, and more advanced than its European contemporaries, heading to sea to project the power and greatness of the middle kingdom across the whole world. This naval fleet could have changed human history. It had the materials and ability to defeat not only the natives the european navies subsequently conquered but also kick the asses of the european navies themselves, but in the end they didn't do either. So of course it's interesting to speculate on what Zheng He's fleet might have been up to.
But as a work of non-fiction the book lacks credibility. The author suffers from the notion that he is uniquely qualified to understand and unravel Zheng Ye's travels because he was once a submarine captain. He also tends to assemble for support a confused but massive hodge-podge of purported evidence. All of it he says favour his one explanation.
He could have kept to a plausible theory (the Chinese went further than we know for certain they went). He has lots of evidence to suggest that someone was travelling before the Europeans did. But he overreaches in trying to argue that the Chinese were fully responsible for everything on his 1001 misplaced items in history list, that we can conclude this fleet was making trips to Antarctica and Australia and South America and everywhere else. If he had stuck to pointing out the flaws that conventional histories of world travel have, the misplacement of items - artifacts, genes, flora fauna that they cannot explain, he may have been better recieved by the academic world. Instead he presents grand theories without the evidence to support them, which require available facts to be read one way when there could be another (way), and thus exposes himself to ridicule and mockery. On the other hand, his sensationalist theories have made him a darling of the media, and he has gained fame and wealth where he has failed to win academic support. This does not appear to be such a bad bargain.