Introductions, Author's Notes, Chapter Quotes and other additional words
Generally, how often do you read the metaphorical bookends to a novel?
I find that I very often will skip an intro by someone other than the author as it's usually little more than "hey, my buddy wrote this and I like it" and I don't usually need to know. Sometimes I will read the intro on a re-read, or if I really love the book, or if the introduction-writer is someone I have heard of.
Contrariwise, I almost always read author's notes. I like hearing about the process of crafting stories, or any addition insight into how the book came into being.
When it comes to quotes in between chapters or song lyrics in between sections, I find it depends on the length and the origin. If it's a short quote, I read it. If I know it's in-fiction quotes, I usually skip it. If it's a long chunk of song lyrics, I skip that, too. I'm pretty sure it's because I want to dive back into the tale and I think of quotes and lyrics as an unwanted commercial interruption.
What are your habits?