Having read Jan Morris's Venice before visiting the city, I've come to the conclusion that it's better to read books about a place or set there when actuallly in situ or back home again - locations mean so much more when you've been there. I looked carefully at all your suggestions of Venetian reading, but for reasons of availability, practicality and mood what I ended up with for my trip over the last few days was Sarah Caudwell's entertaining Thus Was Adonis Murdered - perfect for reading on the plane and in the few moments we were resting our weary legs (we walked miles) between sights. A legal murder mystery in which the crime is committed in Venice but solved by an Oxford professor and a group of his former students - all now barristers - back in London, this was arch, intelligent, intricately contrived and a lot of fun, and I look forward to reading more from the series.
For 'real' Venetian crime, I very much want to start Donna Leon's Commissario Brunetti series, beginning with Death At La Fenice, although ironically we didn't actually get to La Fenice - that's on the list for our next visit - and I walked past the Inspector's Questura without noticing it (there's a helpful guide to some of the books' locations here). I spotted only one bookshop in Venice, in the window of which Ken Follett was very much to the fore; has anyone read The Pillars of the Earth, by the way? 1100 pages about the building of a cathedral rather appeals to me.
Back home again, I've just started Jane Borodale's The Knot - quite literally back down to earth!