Hello again.
I want to add that I've already read this help item :
http://manual.calibre-ebook.com/faq....d-phone-tablet
According to that, I can only "connect" Calibre to my Android device using a USB cable if my device is assigned a disk letter.
That's not the case of my Nexus 7 tablet: I think the device is not assigned any letter by my PC. BUT it is shown in "Portable devices" section on my computer, and when double-clicking it, I can see "Internal Storage", and then I can see several folders in it, including a "Kindle" folder. The path for that folder is:
"Computer\Nexus 7\Internal storage\kindle",
so no "disk letter", as far as I understand.
By the way, I am using a PC with Windows 7 as OS.
So... Is it true that I can't "click and drag" books to my device, or browse books in my device using Calibre?? Is there any "plug-in" or something?
I look forward to your help.