I have calibre on my pc and I downloaded it to use with my sony ereader. Having collected my new Kindle yesterday and been amazed at how easy it is to use, can I use the same calibre with the kindle or do I need a separate one for the kindle? Is there any point in having it for the kindle as it seems so straightforward to use? Will the books I've bought from Waterstones convert to be read on my kindle? Any help gratefully received to this kindle convert!