Here's my response from another current thread in the Repetoire forum about which pieces would help with sight-reading:
A long while back ago, in some school districts in California, USA, they experimented with a different reading technique called "whole language". The traditionaly approach was to learn the sounds of each letter and combined letters' sounds - phonetically. Whole language was different by learning language, not phonetically, but by relating to all aspects of language - reading, writing, speaking, and listening. Phonetically, students would recognize the letters within a word, pronounce them sequentially, and put the sounds together to form the word. Whole language students, when reading an unfamiliar word, could not pronounce it because they did not know how the letters were pronounced. What this led to was the inability for the young students to read at higher levels in upper grades causing their academics to suffer immensely because they were always lagging behind in reading skills.
What is the point of mentioning this?
Did you learn how to read by looking at words in a novel by Dostoyevsky or did you learn the individual sounds of the alphabet and then put them together to say simple words - dog, cat, hat - and then as your skills improved you were able to pronounce more difficult words - lion, tigger, happy, ..., piano, automobile, motorcycle, violin?
Most of us took the latter path. This is also the path that is the most effective for sight-reading music. Learning the sounds of the keys, the placement of the keys on the keyboard,... then more advanced: the duration of notes, playing two notes simultaneuosly, then chords...
If you can read this, that is because you spent many many years reading since childhood. You even know how to write now! Simply amazing! And because there are words written all over - on signs, store names, book titles - your ability of reading was further re-inforced. Now, there is very few words that you can not read but learning them is very simple.
So what is the answer to your question? You must first start with the absolute simplist instruction books - and Master them by sight! Once mastered, you can then move on to more difficult material - and master those as well. Once mastered, you can continue on to more advanced material and ultimately, you'll be able to sight-read music the way you are able to pick up a book and read aloud in continuous flow and not stop to try to figure out how to pronounce the words (notes within a chord).
But since music is not as common as language words, it will be difficult to read the music; another problem, even if there were music written all over town, the piano, unfortunately, isn't an instrument that can be put into your pocket and taken out to play the music you read at any given time. As a result, you must spend countless hours a day looking at the music AND playing it.
The huge library you refer to is useless to your goals if you do not have the fundamental skills to utilize it.
Topic: Sight Reading Techniques?