I know what you mean! The "Science fiction and Fantasy 13130" collection (mostly A4 formatted) holds more than 13000 books; imagine converting all those..."that" was the reason I wrote this program.
There will soon be a 6th version of pViewer, so keep watching this thread. See the pictures attached here
https://www.mobileread.com/forums/showthread.php?t=69435 for a preview.
c.