There are lots of bookstores in Venice. Almost all of them have English-language sections.
Libreria Cluva, attached to the architecture university of Venice (IUAV). M-F Map SC/Pzl Roma
Architecture and art. Many English-language books.
All bookstores have a section on Venice history, architecture, etc.
Museums generally have good selections of related books in their gift shops.
Polo Urban Bookstore, small, addressed to visitors to Venice with guidebooks, picture books, and souvenirs.
Many around the city.
Segni del Tempo
Libreria Acqua Alta
Amusing layout and large collection of used books, books about Venice, and souvenirs, but usually overcroweded with tourists (including groups) which makes it impossible to browse. M-Su Map SM