Why can’t I see an eBook I read in the tolino library anymore?

As soon as you have finished reading an eBook, it disappears from the title overview under “My books” and is moved to the “Read books” collection. These books still appear in the author overview, however. If you wish to mark your read eBook as unread, which will move it back to the title overview under “My books,” open the collection and press and hold the eBook in question, then select “Mark as unread” in the context menu that appears. Alternatively, you can also go to the “Read books” collection and use the function menu (three dots at top right) to select “Mark books as unread” and then select one or more eBooks to mark as unread.