So she has a Kindle and can read in bright sunlight, he doesn't have a Kindle and can not. But seeing hers and how well it works, he is convinced to buy one. "Lets celebrate!" "Sure, my husband is bringing me a drink." "So is mine!" - oh, wait, I see, the funny here is that she might have assumed this man was hitting on her with the celebrate proposal? How daring! That's not the funny? No? Then you lost me, where's the twist?