Archie comics, like Hardy Boys and Nancy Drew novels, are factory made and bland. Superhero comics (which are what I used to do) are far more variable, and contain some of the greatest masterpieces of the artform, beginning with King Jack Kirby.

As for Agatha Christie - a few suggestions:
Pale Horse
Hallowe'en Party
Endless Night
Five Little Pigs
the Harley Quinn stories