The speed at which you can present text to the reader is not the end-all, be-all of the reading experience. In fact, the logical conclusion, of having zero transition whatsoever, is actually a pretty terrible experience. Why do you think people use smooth scrolling on their OS? Transitions are very valuable in producing a good user experience, whether it's a simple horizontal slide as the Kindle iOS app uses by default, or a page turn animation as iBooks uses by default. And if your argument is purely about the speed of the animation, there is nothing about a page turn that inherently requires it be slower than a horizontal slide.

Speaking personally, the iBooks page curl is one of my favorite features of any iOS app, period.

I don't know when it has been introduced, or even if it was always there and I didn't notice, but iBooks also supports continuous vertical scrolling and it IS much faster than looking at an animation that shows a page turn or a slide. The default mode, "page turn" doesn't make any sense. When I scroll through an ebook through the continuous scrolling, the text appears INSTANTLY, without a perceptible delay and since it's continuous scrolling, you don't go from a page to another, but you're always "in between". The concept of a "page" 1, "page 2", "page" 3 itself is no more. It's not a physical book, it doesn't need pages.

This is a case where I recognize the absurdity of pages in e-books, and yet I still like to have them. Pages give you a sense of progress through the book, and act as a proxy for time spent. They're not necessary as part of the presentation of information, or even telling a story, but I do like having them there.

Maybe this is one example of skueomorphism done right, at least from my point of view. An anachronism that helps to make the user feel comfortable with the application, even though it isn't strictly necessary.

I think a better animation would be the page 'lifting' and swiping away quickly to reveal the page underneath. You still get the affordance of turning a page, but with a new and improved SwiftTurn digital method, and without the ponderous neccessity of fake flipping a page.

Ala swipe to unlock, or elastic scroll-ending. Use affordances, rather than limiting real world analogies.

It's a matter of personal preference. A seemingly endless expanse of text seems daunting. I like the idea of pages, they break down the text into more manageable pieces.

Scroll mode was introduced in the just-released iBooks 3.0. And I personally think think a never-ending scroll of text is not a good way to read a book. Pagination is very helpful. I realize other people like scroll mode, but that's a personal preference.