Non-fiction books you read more than once.

If somebody is willing to read a particular non-fiction book twice or more, then it’s at least worth checking out.  And that helps sift the wheat from the chaff in a plethora of books that could be a potentially HUGE waste of time. I must find more diamonds in the rough.  

Also, if you could also explain why, it would help me (and others) understand the appeal that motivates you to read it more than once.

>>16

Yeah, I noticed that too (minus the cynicism). It doesn't really bother me tho, as the question is merely a way of fleshing out nonfiction titles that people genuinely feel is worth reading. And what better evidence of that than having read a book more than once?