From his Q & A with Powells.com:
Share an interesting experience you've had with one of your readers.
A little background: I didn't research my first novel as well as I should have, because after hearing about how hard it is to get published, I didn't think anyone would ever read it.
One day, I received a letter from a guy who said he hoped I wouldn't be mad and then went on to list my mistakes page by page — missing only one obscure error relating to the construction of crack pipes. Not only was I not mad, I immediately printed off a copy of the book I was working on and mailed it to him with a note saying, "See what you can do with this one."
Read the full Q & A.
--Marshal Zeringue