I haven't read the book, but as a production manager for a publishing company for a number of years, I can only say that it is not the author's responsibility or fault that there were errors. It is the copyeditor's responsibility to make sure that two plus two equal four(even in artwork), and the proofreader's responsibility to make sure there are no misspellings. It's nice if the author can catch them, but they rarely do--that's why we hire copyeditors and proofreaders.

As to metric--don't know. Is the author or the book publisher European? The rest of the world uses metric, although there are some in the U.S. that use metric (CalTrans, for instance). All I can think of is that the editor was pushing a metric book to be the first on the block, or to sell to a bigger European market....