There are only two ways to learn to read: "sight reading", and "phonics".
"Sight reading" is not really a system. You simply look at a word, over and over, until you can force it into your long term memory.
Words are learned, one by one, by some visual "cue"; the shape of the words, or the letters, or some other visual key. As you can imagine, it is extremely difficult to learn thousands and thousands of words this way.
How many words do we need?
Studies show, that sight-reading results in a lifetime reading vocabulary of between 3000 and 6000 words. However, the average workplace requires 12,000 to 20,000 words. A sight reader has great problems in a job that requires reading.
Difference between Speech and Reading Vocabulary
To understand this, first we must understand the difference between "speech vocabulary" and "reading vocabulary".
Speech vocabulary is the total number of words we use in our everyday speaking, but also, the words we understand when other people speak. We listen to radio, watch television, we talk to people and have conversations - at the shops, on the phone, all sorts of situations.
So, your "speech vocabulary" can be quite large, and this is an advantage.
Reading Vocabulary is completely different - these are the words that you can correctly identify and understand when you read text.
Studies show that many people can have a good speaking vocabulary, but limited reading vocabulary. A "sight-reading" person can learn the high-recurrence, short words, but have great difficulty learning the longer, less frequent words.