Its not at all unusual for me to look up a word I see in a book I'm reading even if I get the gist from the context. Its almost unheard of that I see a word and say, "thats a word?"
p. 274 of Undertow by Elizabeth Bear: "The sky was already louring, the moon-glow only permeating a few threadbare places in the overcast."
Louring. Never seen the word before.
Go ahead, look it up yourself. (Or, feel free to let me know that you've known that word since the age of three and use it in conversation on a regular basis.)