Okay, so I couldn't think of a book that would be my "least favorite". I usually finish all the books I start even if I don't like everything in it.
"wicked" by Gregory Maguire is actually an okay book and obviously an AMAZING musical! I could see the musical over and over. Anyway, the reason I picked "Wicked" was because though it is a good book, there is just too much sex happening in the book. Sex isn't a bad thing, don't get me wrong. I just think the book is a little too detailed on the sex scenes and sounds like it should fit in the romance section of the library.
It is still a book I would recommend if those extra details do not bother me. I tried to look past it as I read and actually had trouble putting the book down.