I think I am going with Castle Perilous by John DeChancie. Or any of the Castle books, really. Yes, it's silly. Yes, it's a super easy read. Yes, it's not a new, or highly original, or new twist on a old idea plot. But it's just one of those books I enjoyed reading, and still do. It's action packed, funny, has some interesting characters, and is just plain fun to read. And I freely admit to a squeee moment last year when I found the last few I needed to complete the set.
I know, some people I know would say- You actually read those?? But they're so frivolous. They aren't deep. They have no message! They're silly! My answer- Yup, to all!
And isn't all of the above the definition of a guilty pleasure book? The one you enjoy reading, even more than once, but may not actually admit that to other people. Well, I'm admitting it now!