Without getting technical, you can also load books to Kindles and Sony Readers without any software. You just use a USB connection and copy the files directly to the appropriate folder on the reader. Although this is an option, it is probably not the best option as the books are not placed into collections.

I will say that with the newest Sony Readers the Sony Library software works a 100 times better and faster than it did with the older readers. So I think the Sony Library software would probably be your best option as it requires the least technical skills.