There's some legitimate criticism of Guns, Germs, and Steel. Some of the author's key assertions are incorrect but by and large a very well informed and exhaustively researched.

Most of the vitriol around it though seems to have missed the point. Diamond uses the book to argue against the idea of euro-exceptionalism but a loud part of society sees it as arguing the exact opposite.

Basically, what I'm saying is, don't read it as gospel but an exceptional book that examines the way the world became the way it did from a fairly balanced perspective.