While studying in Edinburgh last year, I went to Venice for a week with a friend of mine last March. Armed with both the Lonely Planet Venice and Time Out: Venice guidebooks, we found the Time Out book to be wonderfully helpful. One of the best things about it was that it included (at least, last year's version did) a map of all the public toilets in Venice, which, let me tell you, is a very good thing. The book itself was informative, interesting, and well-written, the advice given was very sound, and, though accurate maps of Venice are notoriously hard to find, those in the Time Out guide were much more helpful than those in the Lonely Planet. I remember reading that the Lonely Planet guides were best for given areas and regions, but the Time Out guide were better for cities, and I have found this to be quite true.
I wrote this review two years ago for the amazon.co.uk website. I haven't been back to Venice since, but having used other Time Out guides in the interim (very high quality as long as they've been published rencently) and remembering how useful it was in Venice, I would still highly recommend this guide.