The iPad, bringer of death, destroyer of Kindles

Allow me to ask a question that is in no way a shameless grab for Google search traffic: If I already own an iPhone (which connects to the Internet and allows me to check emails/update my Twitter feed, all while listening to my musical library and watching downloaded videos) and have no interest in reading books on a tablet (sue me, I like the feel of a book in my hand, something I can read without straining my eyes and mark up with a highlighter/pen), what does the iPad offer me? This is a serious question. What am I spending my $500 on? How is this an upgrade over my laptop? I mean, I get that it’s cool looking and whatever, but what am I missing out on if I don’t get an iPad?