I am reading a book now and it's riddled with mistakes. I am not sure why it bothers me so much!

Part of it is that I'm never sure what to do about the typos. Should I contact the publisher? Do they already know? Am I the only person in the world who agonizes over stuff like this??

Do you find a lot of typos and grammatical mistakes in the books you read? How do you handle it when you find a mistake?