It is not important to understand what you are reading as you read; it is only important to pay attention, to be interested, and to make a note of what interests you. Understanding is for re-reading, when you begin to see patterns, to recognize the important words and images, to work out the plot.
That is to say, a good reader is not someone who gets it right away. Just the opposite: a good reader is someone who can be baffled without panic; who can enjoy the confusion of reading something new and feel the promise there. You cannot begin until you are confused, but as soon as you are confused, you have already begun.