I've just updated the list today, mainly to include another 2 more Chinese bookstores to it.
Of course, the list is not all. There are many more bookstores scattered around Singapore, mostly located in our neighbourhood shopping centres. For example, San Bookshop, which provides rental service of second-hand books in Romance and general fiction genre, with total 8 outlets right now - 3 outlets that I know of are at Kovan Shopping Centre, Singapore Plaza and Funan DigitalLife Mall. There is also a used book dealer at Beauty World Centre in Upper Bukit Timah Road, but I never visit since 2001 as it is a bit off the road for me.
In every one's heart simply lies a special bookshop that never fail to lure you there over and over again. Scary, hah ?