Is every word in a book title capitalized?

Only the nouns are. "Far from the Madding Crowd", "Whisky Galore", "A Tale of Two Cities" "The French Lieutenant's Woman", "Love On The Moor", "The Drowning Tree", "Catch Me When You Can". All books with Words other than nouns capitalised. It seems to be a matter of choice or style - some publishers capitalise every Word, others capitalise the important Words whether nouns, adjectives, verbs or whatever.