Lithium Pro is an advanced upgrade package designed specifically for users of the free Lithium app, which falls under the Books & Reference category. This Pro version unlocks a suite of premium features that enhance your reading and data management experience. By integrating with your Google Drive account, it offers seamless synchronization across multiple devices, ensuring your data remains secure and up-to-date. Additionally, the app provides extensive customization options, allowing you to tailor the appearance of your reading material with custom themes.

One of the standout features of Lithium Pro is its ability to let users modify various visual elements such as page background color, text color, and link colors. This level of personalization ensures a more enjoyable and comfortable reading session. Moreover, the app includes additional highlight colors, giving users more ways to annotate and organize their content effectively. These enhancements collectively contribute to a richer, more versatile reading experience, making Lithium Pro a valuable tool for avid readers and professionals who rely on digital reference materials.

Lithium Pro boasts several distinctive features that set it apart in the realm of digital reading applications. First and foremost, the app leverages Google Drive integration to provide robust synchronization capabilities. This means that users can effortlessly keep their data synchronized across all their devices, providing peace of mind and convenience. Although book files themselves are not currently included in this backup process, the ability to maintain consistent data access is a significant advantage.

Another remarkable feature is the extensive theme customization options available to users. After upgrading, individuals can access the custom themes feature by navigating to the display settings and tapping the three-dots under Theme. Here, they can create, delete, and edit themes to suit their preferences, altering page background color, text color, and link colors. This flexibility allows for a personalized reading environment that can adapt to different lighting conditions or aesthetic preferences. Furthermore, Lithium Pro offers a broader range of highlight colors, as illustrated in the app's screenshots. These additional colors provide users with more tools to categorize and emphasize important sections of their reading material, thus enhancing productivity and comprehension.