Well, as an analogy... I have al large screen TV, and I also have a smaller screen TV. The large one is great where / when appropriate, and the same in regards to the smaller one.
A "smaller tablet to read a book on"... You mean a tablet screen that is the exact same size as the average paperback book on the market today, as well as the average school text book?
Finally, one last word... "Palming". Once you have a device that can be gripped in the palm of your hand while manipulating the screen with the other; or palming it with your arm hanging down at you side even while you are walking down your warehouse inventory isles; or holding it face-out for someone to sign their name on while you are holding their delivery package in the other hand.
And finally, finally: Why the hell did Apple make an 11" MacBook Air?? Who in the hell would buy an 11" if they can buy a 13"? (hint: all the people who want an 11")