Book Cover Decision

After researching book covers, I eventually chose the book I wanted to change the cover of:

 

(Cyberspace Adventure-Terrance Dicks)

This book is part of a series made by a famous English writer who is mostly popular for his scripting in the Doctor Who series on TV. He produced a large amount of books however. I immediately began to generate ideas on how to improve the overall design of the cover. A made several thumbnail sketches and a mind map to decide how the cover should look.