A few years ago I spent one Saturday a month at my local library's book club discussing mysteries.  That first time we were handed a list of mystery writers to help get us started.  I looked through the list, saw an author that I'd never heard of before and read the general summary of what the entire series was about.  Found the first book and on a whim decided not to read the back cover or inside the jacket.  After all, I had to read it anyway for discussion, right?  (Everyone read whatever they wanted but they had to tell about the book they had picked).  What a surprise!  The mystery started out for 3 chapters with the one person I thought was the main character.  She got bumped off in the 4th chapter and her sister who we knew about but never 'met' came on the scene and was actually the main character after that.  When I was done I read the back cover that clearly stated who was killed.  What a let down that would have been had I known before hand.

I haven't read the back or inside jacket of a book since and I find I have enjoyed reading so much more. 

How do I determine what to read next if I don't know what the book is about?  I do read summaries and listen to people who are excited about what they are reading.  I have an on-going list of books to read that sound interesting and label them accordingly: mystery, romance, non-fiction, etc.  So after reading a mystery I may decide I now want sci-fi so I'll look at that list and grab a book.  By the time I get to said book I have forgotten what it was about.  Try it sometime!