Minimalist, airbrushed, colourful and mysterious, what's not to like?
During the 60's and 70's Eyke Volkmer has designed 162 paperbacks in the airbrush styled series "Goldmanns Weltraum Taschenbücher" - see full set here: http://www.weltraumtaschenbuch.de/pages/theproject.html and referring article here: http://www.sci-fi-o-rama.com/2010/02/27/eyke-volkmer/ - also check out http://www.houdinination.com/ which is a good online archive of sci-fi literature.