I took a trip to Waterstones, for inspiration.
I found some really interesting and aesthetically pleasing book cover sets.
A lot of book sets work using specific colour schemes. They normally use minimal colours, to keep them simple and cheap to produce.
I particularly like the black and white paper covers. They all look 3D when you're holding them! They're really clever! I like how type has been used within the images too. The spines are equally as nice as the covers. Again, very simple. They consist of a simple shape which works best with the cover, the title, author, and the logo.