This is the first dictionary I reach for if I want to find a definition of a word. It's also the first book I reach for if I want information on a famous person, or need to know where a particular place is.
In short, it's a dictionary and encyclopedia in one very handy size.
Plus points:
> it's easy to find any of the 120,00 definitions: the letter markers are visible from the outside.
> includes a thorough mid-section on famous people and places
> plentiful grammar and usage boxes (e.g. between diffuse and defuse).
Oh yes, it's also less than £8. A literal bargain.