I can't imagine what one would do with thousands of books on an e-reader, given that you would never be able to find any of them again, since there is no search function for titles, authors, or content AFAIK.
Does anyone really have the time to scroll down thru hundreds and hundreds of entries in the Library? It would take hours to locate a book. Would you want to spend days organizing them into Shelves?
Sorry, but an e-reader is Not a fast computer. Bad idea.