Most libraries are directly outside MRT stations, with the
exception of a few which requires you to walk to don't know where.
Woodlands, Sembawang libraries are examples.
I know of one library inside a mall, Cheng San Community Library.
Alight at Hougang MRT station and walk to the mall. Go to the third
storey. That's where the library is.
Ang Mo Kio library is near Courts (electronics store, not lawyer
courts), if you have been there.
For Toa Payoh library, you have to walk a distance. It's outside
MRT station as well, but I reckon taking a bus would be better. 73
and 105. The one going towards Toa Payoh. Other libraries have yet
to explore. 
