A series is based on a strong concept that ties the book together.
It can be:
- A professional on the job seeing different cases or a super hero, such as Lie to Me or Sherlock Holmes
- A person dealing with a recurring situation that nobody else can handle, such as The Elite where the heroine must compete for the hand of the prince or Angel Fever where the heroes are the only ones who have the powers to get rid of the alien invaders
-A compelling world, connecting a cast of characters such as the vampire world of The vampire Diaries or people lost in an unknown land as in Lost or The Forest of Hands and Teeth where the heroes are one of the few to find hope for humanity.