Here's a fascinating book by a French brain scientist who is elegantly articulate in English. The language is important, because he uses the peculiarities of English spelling, and the consequent difficulties of inexperienced readers to interpret it, to demonstrate how many different areas of the brain must be activated to interpret something as simple as the sentence you have just read.
Stanislas Dehaene, Reading in the brain : the science and evolution of a human invention. (Viking, 2009)
When we begin to read a page of text, we don't take in the whole page or even a whole line, but visualize clearly only a very small section at a time, moving our eyes in rapid saccades. Reading requires rapid and successive interpretations of small sets of visual marks (in alphabetic writing, no more than 5-7 letters per saccade) by neurons from several regions of the brain, interrogating the symbols until the most likely hypothesis of their meaning is established. The very first operation in each saccade is to recognize the symbols as letters (rather than corporate logos, or numbers, or something else) and attribute possible sounds to them. If the symbols invariably represent a single sound (as in Italian or German), it is quickly recognized by the phonics neurons. If they may represent several possible sounds (e.g., the letters "ough" in English), other neurons from other parts of the brain must apply grammatical rules while others evaluate context (the symbols seen in previous saccades) to narrow the possible interpetations.
Recognition of symbols as letters (or phonemes or characters in nonalphabetic systems) occurs in all humans, regardless of culture or writing system, in approximately the same section of the left brain hemisphere (Dehaene calls it the "letter box"), but requires activation of other brain sections to interpret them. Recognition of simplified symbols, or "proto letters", evolved millions of years before the invention of writing, inspired by common forms seen in nature: L, Y, T etc. Even apes recognize such symbols. What humans have been able to do that apes cannot is to learn to give different interpretations to the symbols, that is, to invent writing.
"…over time, scribes developed increasingly efficient notations that fitted the organization of our brains. In brief, our cortex did not specifically evolve for writing. Rather, writing evolved to fit the cortex." Thus all writing systems in all cultures, even Chinese or the many Indian scripts, share common features: combinations of symbols of no more than 4 strokes, arranged in straight, regular lines. All (even Chinese) include some signal of sound. Those writing systems that correspond most closely to spoken sounds (e.g., Finnish, Italian, German) are the quickest for children to learn, English is the most difficult of the European languages and reading Chinese takes much longer. Phonics teaching is far superior to "whole word" approach for enabling the learner to read unfamiliar words.
There is much more to this book, including diagrams of brains and brain activity, a capsule history of the probable history of writing (how the first symbols were invented and how they evolved), anecdotes from the history of reading-brain research, an impassioned discussion of pedagogy, and chapters on dyslexia and mirror writing. It's a very complex subject, but Dehaene is a graceful writer and makes it about as clear as it can be for us non-neuroscientists.
For more on this author, see Overview - Experimental Cognitive Psychology - Stanislas Dehaene - Collège de France