Hi. I use Calibre all the time to transfer my books from my computer to my tablet. I have a Samsung Galaxy Tab A8. I have Cool Reader on my tablet. To transfer my library from the Calibre program on my computer to my tablet 1)connect the tablet to the computer, 2)accept the Allow Transfer data notification that comes up on the tablet , 3)then use the Send to Device button in Calibre to transfer the entire library or whatever book/s you want to transfer. to a designated folder/SD card on your tablet. Hope this makes sense and helps you. Good luck!