Book-worms the world over have reason to rejoice, as booksellers, libraries, tech companies and e-commerce sites all work to drum up new ways to cash in on the e-book reading craze.

As one of the new must-have gadgets, e-readers have taken the populace by storm, with announcements about new varieties and updated versions coming on the market every quarter, as companies tout the success of the devices. 

Just this Tuesday, Tokyo-based electronics giant Sharp announced its plans to launch an e-reader this year that displays text, video and audio content. Earlier this week, online bookseller and manufacturer of the Kindle e-reader, Amazon.com said sales of e-books have surpassed hardback sales in the past three months, even though the number of titles available electronically is far less than titles available in hardback.

Dan Costa, executive editor of PCMag.com, said that although e-readers have been around for some time, the current digital reading renaissance can be credited to the expansion of wireless Internet.

"The infrastructure is just now catching up, and since a lot of these devices are wireless, you can literally take the device out of the box and can go shopping and make a purchase inside of 30 seconds," Costa said. "It allows for more impulse buys," which is something readers like.

This ability to buy new books at the touch of a button, and the devices’ ease of use has given reading a whole new appeal, and as prices for e-readers continue to fall, more consumers are expected to adopt the technology.

In this rapidly crowding e-reading space, keeping track of all of the choices and features available to consumers can be daunting. Tech experts say that before investing in an e-reader, it’s important for consumers to decide which features are most important and where and how they plan to use the device, so that someone who wants to use the device for reading on the beach makes sure to check out the anti-glare E-ink screen on the Kindle, and someone who wants to both read and watch movies looks into the iPad. Here’s a list of some the best-selling e-reading options available to help consumers decide how best to get their read on.

Amazon Kindle

Credited with launching the e-reading revolution, the Amazon (AMZN) Kindle is well-known for its E-Ink electronic paper display, which mimics the look of real paper and wireless connectivity to Amazon’s Kindle store. Amazon recently dropped the price on its second generation Kindle, which is now available for $189, compared to its earlier price of $259.

The Kindle DX, the latest model of the device, which features a larger screen, more contrast for sharper image and text definition, auto screen rotation which allows readers to view newspapers in landscape and is available in graphite, also saw a price cut this month and sells for $379 a month, down from the original price of $489.

Both versions of the Kindle offer free wireless connectivity using Amazon’s "Whispernet" data network, which runs on AT&T’s (T) 3G network and is available in some countries abroad, although some fees are added for international use. The device has 2GB of internal memory, although additional memory cannot be added. The device can play audio files and is compatible with both PC and Mac.

Apple iPad

It’s tough to compare Apple’s (AAPL) iPad to a standard e-reader. The device offers an abundance of functions that more closely align it to a tablet or laptop computer than an e-reader alone. Some tech experts think this new market the iPad has created with a multi-functional all-purpose device, is set to overtake the market for e-readers like the Kindle.

“I think probably the Kindle will not rule the market anymore, since it does basically one thing,” said Nahum D. Gershon, Ph.D., senior member of the IEEE Computer Society.

“There will be lots of competitors, [for the iPad] I believe it’s a big market, and I think there is a big future for this type of device.”

The iPad doesn’t feature the E Ink screen, popular among most fans of e-readers for it’s paper-like properties, but it does support more than one e-reading application. The company’s proprietary reading app, called iBook, allows users to download e-books from the Apple iBookstore, but the iPad can also use apps created by both Amazon and Barnes & Noble (BKS), giving users access to their catalogues as well. Connecting the online booksellers’ catalogues is possible via WIFI or the AT&T 3G network, depending on which model iPad you purchase. WIFI models of the device start at $499 with 16GB of storage, and go up as you add storage space, with 32GB offered for $599 and 64GB for $699. Models of the iPad that offer both WIFI and 3G capacity start at $629 for 16GB, with expanded memory going for $729 and $829, respectively. 3G connectivity comes at a price, however, with AT&T 3G data plans offering 250MB of data for $14.99 a month, and 2GB of data for $25 a month.

The iPad’s host of features, such as the large screen, which is capable of viewing HD movies that can be rented on the device, Bluetooth, mp3 storage, personal photo viewing, email and gaming make it far more than just an e-reader, but fans of the E Ink reading experience will not likely be impressed with the LCD screen.

Barnes & Noble Nook

Barnes & Noble’s proprietary e-reading device, called the Nook, is an Android-based device which features the same size E Ink display available on Amazon’s Kindle, but also has an LCD touchscreen below. The touchscreen reportedly reduces battery life somewhat, but allows users to navigate the device using touch.

The Nook offers a lower-priced Wi-Fi only device that retails for $149, and then has a model that uses 3G and Wi-Fi for $199. Some of the Nook’s distinguishing features are the ability to listen to mp3 files, which can be loaded via USB, and the ability to store photos. The device comes with 2GB of memory, with the ability to add additional memory via SD slot, web-browsing capacity and features Android games. The Nook’s lithium ion battery is also replaceable and the book is compatible with both Macs and PCs.

Some interesting features such as the ability to lend ebooks to friends for 14 days for free, the capability to browse through entire books when inside of any Barnes & Noble Store, and the potential to read ebooks on loan from a local library and read free Google (GOOG) books, make it an interesting competitor for the Kindle.

Borders Kobo

Not to be left out of the e-book bash, Borders Bookstores recently launched its Kobo e-reader, positioning it as a stripped down device that allows users to do just the basics: read books. When it was launched before the Amazon and Barnes & Noble price cuts, it was the least expensive e-reader available at $150. Now that the Wi-Fi Nook is priced at $149, the Kobo has been selling it with a $20 Borders giftcard to keep its pricing competitive.

But the Kobo does not come equipped with wireless Internet connectivity, meaning adding new books requires downloading them to your PC or Mac via the Kobo e-bookstore, and then loading them onto the device using a mini-USB cord. There is no built-in keyboard, and the Kobo is navigated using a bright blue button in its lower, right-hand corner. As the lightest of the bookseller-backed e-readers, it’s a convenient size and still features the 6-inch E-Ink display. The device boasts a 2-week battery life and supports ePub, PDF and Adobe DRM formats, meaning that library e-books could be viewed on the device, unlike the Kindle. The e-reader also comes pre-loaded with 100 free 19th century e-books.

Entourage Edge

The Entourage Edge is probably the best solution for students in the market for an e-reader, as it functions both as an e-book reading platform and tablet computer. The device features two screens, hinged together with the left side using a touch-screen e-ink display and on the right, a standard LCD for web-browsing and video viewing.

Both screens are touchscreens, with the e-ink side allowing the user to pen in notes and highlight, copy and paste text. The LCD side of the device features an Android-based computer, which includes the capability to read and write to Microsoft (MSFT) documents, run apps and it features a webcam. The device uses Wi-Fi to connect to the Internet.

Despite it’s multiple functions, the Edge’s size and weight put it in a different class than the aforementioned e-readers. The device weighs more than three pounds, twice the weight of the iPad and significantly more than the other major e-readers weighing less than a pound. The $490 price tag is also more difficult to justify, especially if you’re just looking to read books. Still, the Edge offers an interesting combination of features and its future looks promising.

“I really like the concept of this e-reader, but price is $500,” said KT Bradford, News Editor at Laptop Magazine, of the Edge. “It will be interesting to see what they do with the next generation.”

Spring Design’s Alex

This Android-powered e-reader offers Wi-Fi connectivity and supports ePub and Google Books, but lacks a tie to a major bookseller. The device features an LCD touch-screen, much like the Nook, boasts 2GB of internal memory with the ability to add more via microSD, plays mp3 files and can play some video. However, the device’s price point at $399 is really too high to make it a tough competitor for the comparable Nook.

“I like the Alex a lot, personally, but its main drawback is that it’s very expensive…and is currently only running on Wi-Fi,” Bradford said. “3G versions might be subsidized by wireless carriers like Verizon and they were talking about that going forward to ease up on the price.”

Sony

Sony (SNE) is no stranger to the e-reader market and its Sony Reader Pocket Edition is smaller and more portable than some of the other big names in the market. The device is priced at $149 and uses the popular E-Ink technology, but does not feature the 3G connectivity or the touchscreen that some of Sony’s other e-readers do. The device is compatible with Epub files, granting access to free Google Books and loaner ebooks from libraries, and it can also display pdf files and word documents.

Other Sony e-readers like the Reader Daily Edition, which features wireless 3G connectivity, a touchscreen and expandable memory compete more directly with the Nook and Kindle in terms of functionality, but the price tag of $299 still makes it a tougher sell.

“Internationally, Sony’s doing much better than in the US and the Daily Edition–it does pretty well and has Wi-Fi but I still would put it behind Nook and Kindle,” Costa said.

On the Horizon

Electronic company Sharp announced plans earlier this week to launch its own e-reader by the end of the year. Barnes & Noble has announced plans to sell alternative e-readers in its stores, in an effort to expand the reach of its catalogue, as has Borders bookstores.

At present, the strategy for content providers like Amazon, Borders and Barnes & Noble, seems to be to create it’s own group of proprietary readers through the sale of the e-reading devices, while also making their respective catalogues compatible with a multitude of devices so it will be available to as many customers as possible. The market is too nascent to determine which bookseller will emerge the market leader, but one thing is certain—the market for e-readers and digital books has arrived and it’s not going away anytime soon.