I went to the book store to look at the real books in store as I am going to design the book cover for a book for children.
At frist, I tried to find them on the Internet, but interestingly, I could hardly find their spines and back covers. Most of the images on the web were only showing the front covers.
The front covers are the faces of books, you should capture the audience at the first meeting.
However, when I am choosing a book to read, I like to look at their back covers, since there are often some short pieces of writing describing books.
I really liked most of the book covers, but there were few which were not my cup of tea. I found that I prefer more hand-drawn like images rather than photograph like ones.