amazon.coms kindle

I have a question for anyone who uses a kindle. Can I download books to my computer not using amazons purchasing service and then upload it to a kindle.

If so what is the best format to use for best reading.

And how does it compare to a purchased copy

The reason I ask is if I'm paying for a book I want a physical copy of it. fuck paying for a digital copy when I can get that for free.

>>5
all of the books i read are written by dead people or almost dead people so it's not that big a deal really