How to Judge a Scifi Book by its Cover

They say to never judge a book by its cover, but sometimes you don't have anything else to go on.  Say you are in a bookstore and you are about to leave on a flight. Uh oh, they don't have the next volume of The Lost Fleet.   You have no other choice but to browse what they do have.  In these cases you can often find the book you have been meaning to read or you could take a chance and Judge a book by its cover. 

I will break this down by three subgenres:  dystopian society, space opera, and military scifi. 

First of all, all three can be judged by the rule of B.  Look for these three things:  Big futuristic looking guns, Babes- of the human or non human kind, and bombs blowing up, because explosions are exciting.  If you can get a book with two out of three you are sure to enjoy yourself at least a little.

Dystopian Society-  You want to see a city in decay.  Whether it falling apart because zombie hordes are destroying the future, Bombed out due to some war, or overcrowded till it is a shanny town, the cityscape shouldn't be bright and impressive.  These covers should be bright and the characters should look grimey and unhappy. 


For space operas, you want large elaborate spaceships and a really cool looking planet. There should be a lot of contrast on this cover.  You want the void of space with colorful planets and explosions. 



For military scifi you are going for simple.  You want a big gun with a big dude holding it, or a space ship engaged in battle.  It also never hurts to have an image of the evil alien agressor.

One day I will write my book and it will have the best cover ever.  A man with a big gun will be clutching a babe with his free arm.  The background will consist of a bombed out city with space ships floating above engaged in battle.  The sky will show a colorful planet in the distance.  With that cover the book won't even have to be good. 

Did I miss something?  Do you have examples of me being right and/or wrong?  Let me know in the comments.