How do digital comic store apps like ComiXology or Kindle handle subscription models for comic reading on iPad?

Apps like ComiXology (integrated into Kindle) and publisher-specific apps (Marvel Unlimited, DC Universe Infinite) often operate on a subscription model. This grants users access to a large portion or the entirety of their digital library for a recurring fee (monthly or annual). Purchases made through these platforms are typically tied to your account and accessible across your devices, including your iPad.