I used to love Gould's at 536 King St, now it's gone. Another one for me was buying classics and seconds/rejected (but good) books for cheap at the Basement Bookshop near the Railway Square, that's gone too.
Sapphos at Glebe is good and still around.
Where do you go to buy books now?
Dymocks in George St. Its like 3 or 4 stories with a cafe & armchairs.