Unconnected with the OP, but connected with grammar: my books (paper and electronic) need to be of a certain standard, or it jars me out of the story. One example that sticks in my mind, to the point that I almost set the book on fire, was a book written by an American author. His inability to insert the word "of" after the word "couple" ruined my enjoyment of the book (such as "a couple minutes", "a couple days", etc). I had no problem with it being part of character dialogue, but the laziness of it in-text irked me every time I saw it.
Phew, I've bottled that up for years.
