Can I add, I have a pet peeve around hair. Some authors seem to love their characters to have really long hair, and yet have no idea how much work it is to keep tidy or how to manage it realistically. I like having longer hair but it is more work, it does take longer to dry and it is more difficult to manage.
I was reading one of Mercedes Lackey's less good books and got fed up of the number of men with immaculately kept waist length silver hair and the lengthy descriptions of the things they braided into it. Not everyone needs to want hair down to their rear and it was just infuriating to read. The Anita Blake books are quite annoying for this too as all the men appear to have excessively long and well groomed hair.
I also hate it when authors get things wrong that indicate a complete lack of research. I read the first of the "Left Behind" books which had a chapter set in London. This indicated that the authors had done no research on British police behaviour, rank structures and organisations (we don't have captains, nor do the police drive sedan cars), language and speech patterns (people working at banks in Canary Wharf are unlikely to call someone Governor) or the way pubs operate. I know it's not a major objective of the book to paint an accurate description of London life, but it completely threw me out of the story to see such glaring errors in it which could have been corrected fairly easily.