I am late to the party!
We have spent a total of nearly 6 weeks in Venice, over 3 trips: our honeymoon in 2003; a month-long stay to celebrate our retirements in October, 2013; and a September visit with family members prior to going to Rome. We had plans to return on our Italy trip last March, but we all know what happened with that.
I highly endorse the recommendation for John Berendt’s book, the City of Falling Angels. I have read it’s 3 times and keep finding more to like.
Of course we have visited most (or all?) of the famous sites, but our favorite thing to do now is just walk and explore. During our month-long stay we aimed for 8-10 miles of walking a day, and rarely used the vaporetto. We did consolidate all our island-hopping into one 24-hour period (noon one day til noon the next) and put a 24-hour vaporetto pass to good use, including a circuit around the outside of the island, with stops at San Giorgio and Giudecca to look around; a short visit to Murano with a “sunset cruise” on the return (timed just right): and a morning visit to the garden island of Sant’Erasmo for hour of walking among the farms. Next time we might rent bikes and take them over for that, as the island is large and flat. (This last is something to be left for a long-stay Venice trip, not one of a few days.). We could not fit in a visit to the isle of San Servolo on that pass, so bought tickets another time. San Servolo is the home of a former insane asylum, now a medical museum we wanted to see, but we did not realize one needs advance reservations so all we could do when we arrived was walk around and enjoy the views. Interesting, but again not something for a short visit.
As for walks, we too are Donna Leon fans (I actually saw her walking with a companion from the train station into the San Marco area. I was going that way myself, so I ducked in behind them, not to be nosy but because they were so good at negotiating the oncoming foot traffic so smoothly. Her companion was a gorgeous young man with long hair in a man bun. Does she have sons?
Anyway, for walking inspiration we used a book called Brunetti’s Venice which has 12 detailed walks through different neighborhoods and past landmarks you will recall from the books, including some of Brunetti’s favorite haunts. Each walk has passages from the book relevant to the places you will walk past. It is lots of fun.
https://www.amazon.com/Brunettis-Venice-Walks-Best-Loved-Detective/dp/0802144373
You should be able to find a decent used copy.
Also take a look at this walk on the Venice Insider website:
https://www.theveniceinsider.com/donna-leon-brunetti-venice/
I will recommend an apartment agency if you are interested. It is Venice Red House, locally owned by Venetians Marco and Caroline Malafante. We rented our month-stay apartment from them, a nice big one with a rooftop terrace in a great location. And we booked a smaller one near the Peggy Guggenheim museum for our stay last March, which we unfortunately we had to cancel. They refunded our deposit fully and immediately, unlike some rental agencies. I respect their business ethics (and like their apartments and their prices) and will definitely rent from them if we are able to return.
I have looked at other agencies (Views on Venice and Truly Venice) and rented from the former for our last visit and it was fine, but more expensive. Also these agencies are foreign-owned (one is British and the other is Swiss). I prefer to stay with the Venetian company from now on.