The e-books on the iPhone were usually stored under the folder ~/Library/Controllers/comapple/Data/Library/Library. The specific name of the folder may vary depending on the device model and system version, but it usually contains multiple sub-folder, each sub-folder storing a different e-library. For example, on my iPhone, the subfolder for e-books is called Library-1085, which contains two e-book files called Book1 and Book2. Please note that the location of the e-book file may change due to the update of the Apple operating system. Therefore, it is recommended to check the system update of the device to ensure the accuracy of the location of the e-book file.