Is this dialogue okay for a book?

It's not bad. I like that you are descriptive after the dialogue, but you should try mixing it up a bit. Have some dialogue thats broken up by a thought Like "Really?' Max replied, unable to form a clever response ",....." Or unspoken language, like a nod of approval or something similar. Dialogue is good but I tend to like things that keep the story going rather than pure back and forth banter. Great start though! (: