I was not surprised at the bold character that Kate Winslet creates in Hanna Schmitz. A woman with extreme passions, unashamed sensuality, yet she hides secrets that are tormenting her.  

After helping a young man who is sick with Scarlet Fever, Michael Berg,  played in his youth by David Kross, she starts a love after with this teenager twice her age. As the title suggests, he reads to her in the afternoons when he visits before they make love, including classics like The Iliad and Odyssey by Homer.  It will affect the rest of his life and hers in many ways that only the passage of time reveals in the movie.  One day Hanna disappears and the Micheal is left  to put his life in order.  8 years go by and as a law student , Michael is attending a war crimes trial only to see Hanna as one of he defendants and he discovers something Hanna is hiding that would make a great difference in her defense.  Instead of mounting a defense she takes the main responsibility for a crime that was not all hers.  The brunt of the punishment is hers alone.  

A new and different relationship with Michael as an older man, played by Ralph Fiennes  ensues while Hanna is in prison.  He plays a stoic character, emotionally damaged, yet quite, reserved, a successful lawyer, and still in love.  

The story, the characters, are all almost spellbinding.  For those of you that are tired of the "older men" always seeming to team up with the younger ladies, this story is the opposite, the older lady has the affair with the younger man.  Not that is makes it any better, but in the context of the movie and story, the affair makes sense in it's own way.  Both Kross and Winslet make you believe it is the real thing and more than just a wild fling but true love.  

There is more than just a secret, but a great complex story hidden in all of this drama, in some ways a tragedy.  I'll leave all the complex interpretations to you.

I enjoyed it and the performances.