What does it mean when a guy and a girl have the following conversation?

Girl:
“Hi there!
I have been yearning for you to know something that I have in my mind and I think this is the right time to offer my honesty to you. A whisper rose up from deep inside my heart and I must listen to it. I would like to share my heart with you.
I had been thinking about you and am appreciative of you as in the form of you, I see a person who is wonderful, inspiring and a pleasure to be around.
I think that I would like to know you better.
Hope to hear from you!”

And Guy ( in response) :
“I am an open book, you know me already :) ”

What according to you does the guy mean when he writes this?