Musing Mondays (5)

Musing Mondays is a weekly event, hosted by MizB at Should Be Reading, where you are asked a book/reading related question and you answer with your own thoughts on the topic.
If you come across an unfamiliar word, do you stop and look it up right away?

It really depends on what kind of book I'm reading. If I'm reading a classic book, there'll usually be little numbers that lead to a glossary so I'll look there and then go back, but if I'm not reading a classic book or a book with a glossary, then I make a guess on what the word means and then move on.
Do you look up words that are unfamiliar?