Need to know: Save up to 77% on a one-night stay for two at the Blue Rainbow Apartments; Includes a fab location in the heart of the city, as well as wine in your room on arrival; Based in the heart of Edinburgh, overlooking Queen Street Gardens; What & why: Anyone who's read one of this decade's hottest books, 'One Day', will hold a special place in their heart for Edinburgh - the very thought of Arthur's Seat has us welling up! But even if you haven't read it (or seen the film), there are a…