One example is Starship Troopers. I've always found, as long as the book is well written to begin with, that it added to the experiece of reading the story (if not to the text itself). One of my friends said that he enjoys them, and if he finds after a few that he doesn't, he merely skips them and they cause him no bother. This technique seems to be used more in mid-twentieth century novels, and seems to be much more obscure today.
My question is this - when literary quotation asides are used, do you usually consider this pretentious, or do you enjoy the use of metaphor? What other books do you know of that have used this device?
When I run across these things I usually gloss over them. If the story is well written I'm too eager to get back into the story to take the time to read the little passage. If the story is excellent, I might read these on a reread of the book. If the story is not all that great, these seem pretentious.
Sum up, do it if you want to. It's something readers know they don't have to read so if they don't appreciate the style you haven't bothered anyone. Those who like it (and I'm sure there are many) will have the opportunity to read them and see how they play into your work.
One interesting take on the idea: David Gerrold used made up quotes for one of his series. So you get stuff like: "Conversation is a lot like landing an airplane. Any conversation you can walk away from was a good one," or "If all you have is a rope, everything looks like a neck."
(For more, see: http://www.gerrold.com/short/page.htm )
Whether real or fake, I think quotes like that are similar to the "Easter Eggs" that Survivor mentioned in the "clingers" topic. They are the types of things readers who liked the book might go back and read without reading the rest of the book again. They add flavor, but they propbably should not be integral to the plot because some people skip over them while reading.
As for song lyrics that are still copyrighted, you can do that if you're going to sell like Stephen King. It's expensive to get the rights, and publishers genereally don't want to do it (especially for multiple quotes) unless they know the book will be a big success.
Connie Willis did a interesting twist on this in her novel Passage. Each chapter started with the last words (i.e., what they said on their death bed) of a famous person. Very fitting with the rest of the book, and sort of delightful factoids unto themselves.