There are two pretty good second-hand shops in Chania.
Both have a good selection of English (and other foreign) books which
cost a fraction of the price of new ones.
If you are lucky (and if you like that sort of thing) you might also find some old stuff (not antique!) such as early 60's kitchen equipment that nearly belongs in design museums.
One shop is near the central bus station (KTEL)
To Kelepouri Smirnis Street 26A no telephone, normal shop hours
The other one is near Splantzia square (that's where the church with the minaret is)
To Bazari Daskalogianni Street 46 no telephone, normal shop hours
Both shop are run by English or English speaking foreign residents