Have you tried deleting the books.db file on the T2 (and the one on the SD card too if you are using a card) in case there is a database corruption issue impeding the loading of books? You will not lose the books on the reader, but things such as last page read will be lost.
In case method is not known - connect to PC via USB cable, search for books.db, delete it (one on the card as well, if applicable), disconnect from PC and turn the reader off (right off, not sleep). Turn the reader on again and leave it to automatically rebuild the books.db file.
If that doesn't work, have you tried a full hard reset
https://us.en.kb.sony.com/app/answers/detail/a_id/36559 ? You will lose everything on the reader when this is performed.
If none of that works have you tried reformatting the readers memory (use the method in the reader's menu)? You will lose all books, etc on the reader when doing so.