In his book "1421 - The Year China Discovered America" Gavin Menzies gives his view on the chinese discoveries. He is not historician, and his book could go more to the 'not-so-serious-history' part of the shelves in the library, but this does not discard his work.
As a submarine captain he travelled the seas which he describes, and as he was born in China and, obviously, conected to it throughout his life, he seems to be well equipped to reveal some of the dark spots in Chinese history, which emerged as China closed to outer work in 15th century.
As everyhing else, Chinese did this closeing thoroughly, and little of knowledge about outer world was saved of destruction then. But, as there was so wast a wealth of it, G.M could find some evidence for his claims.
Sure, it puts our critical mind to work, but it is always worth exercising it.
The book is written in a highly readable manner, and its layout of proofs tends to be documented, so anyone can check. Some assumptions of G.M. are obviously too stretched ot limited ones, but, then, this is why the book is given to public, that it would process it and give counter-proofs or corroborations.
I enjoy reading it as I was enjoying reading Cook's diaries 25 years ago :-)
And it is growing: on http://www.1421.tv/ online Alexandrian library is building the book further, describing ther discovery of the world by Chinese.
I find it very interesting concept, "research program" in an Imre Lakatos' way, we could say. "Proofs and refutations" of Popper could also be written about it, one day. Means, I like the attitude, Menzies is somewhat old-fashioned in his scientific method, as a sailor of the old school should be. "Novel", New Age approach would be to submit "revalation", but he rather submits his findings and proofs, ideas, and with it submits it to criticism and attempts of refutation. I think this method is good for historical research today. Let's see if he'll succeed to move the public opinion beyond current belief, in fact, beyond curent boistering of Europeans as these who "discovered" the world.