I read the following books from 1963 (age 10) to 1969, with a few stragglers in later years.The Murder of Roger Ackroyd
The Mystery of the Blue Train
So Many Steps to Death
A Murder is Announced
The Hollow
Funerals Are Fatal
Murder in Mesopotamia
Death on the Nile
A Pocketful of Rye
Dead Man's Folly
The Mirror Crack'd (the only one I actually figured out whodunit)
The Pale Horse
The Moustrap (and Other Stories)
Thirteen at Dinner
Mrs. McGinty's Dead
Hickory Dickory Death
The Mystery of the Orient Express (originally, The Mystery of the Calais Coach)
The 12 Labors of Hercules
Appointment With Death
Curtain
