And just to buck the trend - I detest Calibre.
I absolutely hate the way
IT decides how to organise your library - I do not want every book to be in it's own folder and there is no way to change it.
At least Reader has the decency to leave my folder structure alone - and to be honest I've never had a problem with it when managing my 650.
I do have Calibe on my machine but I only ever use it for the essential AA operations: load a book - work on it - remove from Calbre. That way I can keep my library tidy the way I like it.