I've read five Queen related books:
'The Early Years',
'Freddie and Me'
'Freddie Mercury - The Definitive Biography'
'Freddie Mercury' (Peter Freestone)
'Mercury and Me' (Jim Hutton)
The Early Years' was great, but not for the casual fan as it was dedicated almost entirely to the members' individual and collective history before 1973.
'Freddie and Me' was a graphic novel telling the story of the author's life through his Queen fandom - probably not what you're looking for.
'The Definitive Biography' was almost exclusively a retelling of material that is already out there in other forms including the Freestone book , the Hutton book and video documentaries and public record that proceeded it. The only new stuff for me was the chapter related to Barbara Valentin and her sometimes slightly sketchy claims, and some gossipy and rather salacious details about the compulsiveness of Freddie's 80's sex life. I read this book last, so it was kind of a rehash for me, but if you haven't read or seen much else that won't be the case for you.
The Freestone (friend and employee) and Hutton (friend and lover) books are good counterpoints to each other, because the times periods they cover overlap and both men were in Freddie's inner circle. It's interesting to see the same events from just slightly different perspectives. Like Brian's stereo photographs, the two read together make the Freddie of 1985-1991 pop more than if one had read only one or the other. Both men loved Mercury dearly, so both suffer slightly from rose coloured glasses syndrome to a point.
From those that have read other books, what else is worth looking at?