I'll second this recommendation, though I read it some years ago - I've just recently finished Crowley's history of the Venetian Republic, which is also very good.
Whilst I'm at it, and because I never miss a chance to say so - Barnaby Rogerson's 'The Last Crusaders' is superlative. Covers a similar period, and I can't recommend it highly enough. If you only ever read one book on the period, read that!