Marvin alternatives
Marvin's unique Artificial Intellegence reads your books with you and helps you discover amazing things about them. Build summaries in seconds and pin any web content to your books. Marvin has hundreds of amazing features and refinements designed closely with readers who are passionate about their books. Control page warmth, reading timers, multi-columns, themes and dozens of other reader-friendly features. The best Marvin alternative is Apple Books
Slightly disappointed this version is a separate application and another $5 but it is worth every penny and I'm happy to support its development.
Great features like Dropbox support, sync location between devices and a Calibre plugin make this shine. The customization options are massive.
If you buy only one eBook read application make it this one.