In this post I pointed out an error in van Perlo's Endgame Tactics. Shortly afterwards I sent an email to New In Chess, figuring that telling the publishers about the mistake was probably more useful than just shouting into the great void of the internet.
I'm happy to say that I got a perfectly polite reply, which I see no reason not to report:
"Thank you very much for your contribution. You are absolutely right, of course. It's very strange that we haven't noticed this with our checks!
Unfortunately, by the time you sent us this mail, the third edition was already at the printer's. So your correction will have to wait until a possible 4th edition."
Maybe one day the book will be considered an all time classic, and I'll be able to tell the grandchildren about the time I helped to fix it up...
(In the unlikely event that anyone at New In Chess does feel that I've broken a confidence here, let me know and I'll happily delete this post).