An e-book (or ebook, or eBook, depending upon who you ask) is the digital equivalent of a paper book. According to KiwiTech, the publishers of Classics2Go, the market for eBooks has increased more than 60% over the last six years and growth from this point is expected to be very strong.

We can reasonably connect the start of this burgeoning market to the release of the Amazon Kindle in 2007. Strong sales convinced some wary readers that this was a viable option. You could carry a few hundred books under your arm, and the reading experience was, well, acceptable. Going on a long trip? Wouldn't it be nice to take about 20 pounds of paper out of your luggage?

2007 also marked the introduction of the iPhone; it took about a year for eBook apps to appear on the iPhone. Now there are so many of them that finding the right one for your purposes can be a confusing prospect. I would like to clarify all this a bit by categorizing the four types of eBook apps, at least so far, and letting you know what you can expect from each.

In deciding upon an eBook reader you need to consider: what sort of material you will be reading, how much you are willing to spend (if anything) and the quality of the viewing experience.

Last year, Andrew Kazmierski and Phill Ryu released Classics (iTunes link). Their idea was to take a bunch of books in the public domain, 22 in the current release, and control all aspects of the user experience. We covered the first release of Classics upon its original release when its price was $2.99. Since then, the price has dropped to .99 and the number of books has increased.

This app looked so impressive that it was featured in an Apple iPhone commercial. Upon launch, the reader is presented with a nicely rendered wooden bookshelf displaying colorful dust jackets. Click on a book and start reading. There is no wait, since all the books were downloaded with the app. Future updates bring more books. The books are all the kind of classics that are on school reading lists ranging from Frankenstein and Dracula, to Hound of the Baskervilles.

The feature set is slim. Tap the right side of the screen or swipe right to left and the sepia toned pages turn using a pleasing animation. There are two buttons on the top of the screen. One brings down a maroon and gold bookmark and sends you to the bookshelf. When you click on the book again, you are brought to where you left off. The second button takes you to a table of contents. The bottom of the screen tells you the name of the chapter you are reading and what page you are on. The top of the screen displays the title of the book. Illustrations in books like Alice in Wonderland are nicely rendered, and the text is attractively formatted. A change in color of the title bar gives you an idea of where you are in the book.

Tuesday's iPhone OS 3.0 announcement has left the interwebs even more iPhone-obsessed than usual. If you find digging through all this information overwhelming (or, if like me you were out of town when OS 3.0 was announced), check out this round-up of news, opinions and videos. The only thing missing is a beta copy of OS 3.0 and that's already floating around various torrent sites.

If that's not enough, be sure to check out our continuing iPhone OS 3.0 coverage.

Watch the OS 3.0 presentation -- Were you left off the invite list too? Check out the video in HD or SD at the link above or in iTunes [iTunes link] as a video podcast.

Engadget's iPhone OS 3.0 Hub -- Engadget has a whole page dedicated to their furious and hands-on iPhone OS 3.0 coverage, including this video walkthrough.

What Apple Didn't Announce -- Apple's iPhone OS 3.0 presentation didn't answer every question or address every iPhone issue. Our old friend David Chartier tackles what was left out.

SDK 3.0 brings more NDA fun -- Much to the chagrin of many iPhone devlopers, the NDA is back for SDK 3.0. At Arstechnica, our pal Erica takes on what this means for developers. Let's just hope the NDA is lifted as soon as 3.0 is officially released.

OS 3.0 Screenshot Pr0n -- Pfft, what NDA? iLounge has put together a great gallery of iPhone OS 3.0 screenshots, showing off what's new and improved. Love it.

iPhone OS 3.0 vs. Android -- Lifehacker has a pretty neat comparison of features that are currently avaialable in the iPhone 2.21, stuff that's coming in OS 3.0 and what's available and coming for Android. As someone who has spent a LOT of time using both the iPhone OS and the T-Mobile G1, I'd just add that hardware and UI is actually just as important as "features" when comparing the two platforms. Right now, the iPhone absolutely cleans Android's clock -- despite having fewer "features" -- because the hardware is better (that G1 keyboard is terrible), the UI is more thought-out and the third-party software is better by leaps and bounds. (hat tip, Gruber)

Future iPod/iPhone models referenced in latest betas -- The latest iPhone OS 3.0 SDK includes references to future iPhone and iPod models (3,1) and two other unknown devices.

Now that laptop case manufacturers have had a few weeks to react to the new MacBook, they've started to release an array of sleeves that fit perfectly around the MacBook's refined curves. There's something for everyone here, whether you want a sleeve with a little more padding than usual, a sleeve that makes a colorful statement or one that keeps your nether regions nice and cool. Read on for the round-up.