Maybe tell him that you received it (and thank you, insert compliment of some sort here to acknowledge the effort and all) and you are going over it, thinking about what you feel and think...and you are not ready to respond at the moment... ?
That's what I would do, 2.5 cents and all...
In the depths of winter, I finally learned that within me there lay an invincible summer. - Albert Camus
Uncertainty is the very condition which impels people to unfold their powers.-Eric Fromm