I know this isn’t QC here, but it just needs to be said: thank you that your books live up to the name of the publisher!
Although not every book’s content might be valuable to every reader (though I still have to come across a useless one), the quality of the product as such has never failed to deliver.
After just returning a complete lemon from a long-standing chess publisher (and author) I really needed to express my appreciation, and our front runner here should have a slight connection to QC. 
That other book has lots of mistakes that are completely inexplicable by today’s standards, like wrong side to move in the diagram, wrong chess notation like check marks “+”, wrong annotations like “White is better” when it’s clearly Black, or variations that don’t make any sense at all, probably blindly copied from a supposedly 2100+ game in Chessbase, where not even a 1000 Elo player would make those mistakes (like not capturing directly your opponents only remaining pawns but moving away from it and lose). It was the only time I ever contacted the publisher to complain. Their answer was as disappointing as the book.
So thank you QC for raising the bar for books, as KCT does for online training. 