Where in the brain is meaning extracted from visual information?
The short answer is we don't know for sure. Look up "alexia" and "agraphia"; pinpointing the regions of the brain that, if damaged, interfere with reading might give some indication of the cortical regions involved.

Visual cortex (back of the brain) is obviously necessary for the general population, but it's clearly possible for blind people to learn to read without vision. I'm not aware if blind people require an intact visual cortex or not.

There is a nice study showing that semantic information is present in a very compact form in the hippocampus: Invariant visual representation by single-neurons in the human brain.
Quian Quiroga R, Reddy L, Kreiman G, Koch C and Fried I
Nature, 435: 1102-1107; 2005. PDF