How old was Agatha Christie when she started writing books?

probably in the 13 and up because you really have to think about the mystery that's going on so you can't be to young to understand whats going on

However, many people decide to read Agatha Christie before that age and there are many fans who gained their introduction at an earlier age than 13. Often the introduction comes at school or as a television or film version.

Alsonicenoodles is 11 and i just finished Murder on the Orient Express

it is awesome!!