Paris is and - even after London - remains my very favorite city. There is something so magical about the place. I really love everything about it.
As for guide books, I swear by Lonely Planet and Time Out guides. The Lonely Planet Condensed was THE guide we used throughout Paris. It was wonderful.
There are 2 new guide series that I haven't used but am very interested in:
Walpaper City Guide from the publishers of the hipster magazine and from the fantastic Phaedon press.
and
The Hedonist's Guide which MUST be good.