I can thoroughly reccomend the Time Out guide to all those visiting Barcelona. It has very clear maps of the city and surrounding area as well as maps of the Metro and Local train networks, (others we saw just had the Metro one).
We found this the best guide for details of excursions from Barcelona, it suggests train and bus lines to use and a price guide in Euros for attractions.It gives some excellent background information on Barcelona's main sights, suggests walks and even lists the top ten 'scams' to watch out for.
There are also extensive listings of bars, hotels, restaurants, shops etc etc. All in all an excellent buy!