Well, in the US at least the skin color and gender of the author doesn't have an impact on the worth of the book, but if all the books you read are by white men, as in this case, then your perspective on the world is inherently shaped by white men.

There's a lot to be said to being exposed to different perspectives. And no one knows what other things Bill Gates read this year, but that the best are all white men is a little...disappointing I guess.