If anyone sees a book with bad grammar or a bad plotline (or if I write something with improper grammar or a bad plotline), it's important to say something because no one wants to continue reading a book with shitty content.
Or just stop reading.
BUT NEVER, EVER be mean about it.
Saying something like, "Hey, I realized that you continue to [do this] incorrectly. I just wanted you to know that [this] is the proper way to write it."
That will get you a positive response almost 99% of the time.
Please.
Thanks.
Have a nice day.