Really, Agatha?

When The Murder of Roger Ackroyd was named best crime novel ever, I opined on Facebook that of course it isn't -- Gaudy Night is. As it happened, I hadn't read Ackroyd -- I just knew it couldn't beat Gaudy Night! But then I thought, well, I should probably give Ackroyd a try. So I picked it up at the library.
( Vaguely spoilerish talk below )