Follow these steps to cancel your subscription:

On iOS 12 or more recent:

  1. Open the App Store.
  2. Tap on the picture in the right-hand corner.
  3. Select "Manage Subscriptions".
  4. Choose Le Bonheur de Lire and tap "Cancel subscription".

On any previous iOs:

  1. Open the Settings icon on your device (the grey one).
  2. Scroll down to iTunes & App Store.
  3. Select our iTunes ID or login.
  4. Enter your password.
  5. Scroll down to "Subscriptions".
  6. Find Le Bonheur de Lire
  7. Tap "Cancel subscription"

The official Apple step-by-step is available here.