Yes this is exactly what i mean BterRed, but when you have to categorize 10 000 books opening them adds up, so I use Sumatra PDF reader, it can read almost(pdf,djvu,epub,mobi...) all formats and its super fast.
So open up a book with "v" shortcut
move to the next one
automatically closes previous one
opens next one
also I have dual monitor so it makes it a little bit easier
Thanks for the replies, appreciate it.