I usually read some of them but not always all. In some cases, these parts are critical and may be fascinating, of course. On of my ex-boyfriends is an author, and when he writes a Preface, it is certainly worth reading. One tells about his two years of research before he began actually writing the first edition, his health and family problems that delayed the third edition nearly two years, etc.
Huh? i skipped the first part of your sentence.
If the preface talks about the book's history context, I read it... but the think is I'm really careful about that, because sometimes you find prefaces that are actually resumes. Can you believe it? They RESUME the book, at the beginning, before you start to read.
What a disrespect...
I read the introduction then go to the first chapter. If the writing style is easy (I have dyslexia and hate small font and crappy style) I'll finish the book.