Lithium Pro is an advanced upgrade package for the free Lithium app, designed specifically for book enthusiasts who demand more customization and functionality. This premium version requires users to have the base Lithium app installed, which then unlocks a suite of powerful features.

Key functionalities include automatic data synchronization across devices via Google Drive, allowing seamless access to your reading materials wherever you go. The app also offers extensive theme customization options, enabling users to personalize their reading experience with unique color schemes. Additionally, it provides expanded highlight colors for better annotation management.

Ideal for avid readers and students, Lithium Pro enhances the reading experience by offering professional-grade tools that cater to both casual and serious users. Whether you're managing multiple books or conducting in-depth research, this app ensures your content is always accessible and visually appealing.

The standout feature of Lithium Pro is its robust synchronization capability. By leveraging Google Drive, users can maintain consistent access to their reading data across all devices, ensuring they never lose their place or annotations. While book files themselves aren't synced, all associated metadata and notes are securely stored.

Customization reaches new heights with the ability to create, modify, and delete custom themes. Users can adjust background colors, text hues, and link appearances through an intuitive interface found under display settings. This level of personalization allows for optimal readability and aesthetic preference.

Additional enhancements include an extended palette of highlight colors, providing more nuanced ways to categorize and prioritize information within texts. Future updates promise even more features, making Lithium Pro a continually evolving solution for sophisticated readers seeking comprehensive control over their digital library experience.

When it comes to e-books, the size of the library and the authenticity of copyrights are crucial factors for any avid reader. Lithium Pro ensures that users have access to a vast collection of e-books, all verified for copyright authenticity.

The app leverages Google Drive to keep your data backed up and in sync across multiple devices, ensuring you never lose your place in your digital library. Although book files themselves aren't currently backed up or synced, this feature provides peace of mind for your reading progress and settings.

By integrating with Lithium, the free counterpart app, Lithium Pro activates advanced features that enhance your reading experience while maintaining legal integrity and respect for authors' rights.

Format compatibility is essential for readers who switch between devices or prefer different file types. Lithium Pro supports a wide range of e-book formats, making it versatile and user-friendly.

After upgrading, users can customize their reading experience by adjusting display settings. This includes changing page background color, text color, and link colors through the custom themes feature found under Theme in display settings.

In addition to offering more highlight colors as shown in screenshots, Lithium Pro promises future enhancements that will further improve format support and overall usability.