Calli, Campielli e Canali is generally agreed to be the ultimate map of Venice. With this book in hand, you will be able to find even the most out-of-the-way places in Venice.
However, it is distinctly more difficult to carry than the average map, because it is in fact a true book of 226 pages (22 x 23 centimeters). In addition to being a explicitly detailed street guide, it also contains descriptions (in English) of all significant private and public buildings, dates of construction, family, and architectural style.
For the average traveller, this book is probably overkill (Calli, Campielli e Canali is as labyrinthine as the city itself). But for anyone planning a long stay or who wants to travel “more deeply” into Venice, Calli, Campielli e Canali is the map book to get.