|99% of my heavy criticism of computer book authors and their editors is directed towards English language textbooks. They are most certainly no better than the translated ones.
I guess that part of the problem is that major parts of the English speaking world (read: in the Us of A) do not read very much any more. Their critical sense to reject (sometimes very) bad books, from a language, editorial and presentation point of view has worn out. They do not know how to distinguish a well written book from a crappy one. So the fraction of crappy books is steadily increasing.
My impression is that the average IT textbook written in other languages (my experience is with Scandinavian languages, but I suspect that it holds for a lot of other languages) is written under a lot stricter editorial control, and is a lot less smudged with 'edutainment' elements, going much more directly to the point. So the number of pages are about half.
Originating in the US of A has not in any way been any guarantee for quality for an IT textbook. Quite to the contrary. When I feel the temptation to dig out my marker and my pen to clean up the text, I often think of how I could reshape this text into something much better in a Norwegian edition, half the pages. But at the professional level I am reading new texts today, the market for a Norwegian textbook is too small for it ever to pay the expenses. Making an abridged English version would lead to a lot of copyright issues.