There are some notable well-reviewed alternatives to the Kindle, and likely more to come. Competitors with built-in front-lighting include the Nook Simple Touch with GlowLight e-reader, whose price was dropped to $119 when the Paperwhite came out, and the Kobo Glo, which is priced a little higher at around $150. Both feature IR touch-screens and E Ink displays. The Kobo matches the Paperwhite's resolution, whereas the Nook's resolution is that of older Kindles. The Nook is lit via LEDs at the top of the screen and the Kobo Glo via LEDs at the bottom of the screen. Both reportedly have fairly even light distribution like the Kindle Paperwhite. Both are ad-free. The Nook site makes a point of saying that it is both ad-free and comes with a wall charger.
Another possible choice is the Sony Reader PRS-T2, which has IR touch-screen interface and E Ink display. It doesn't come with a built-in light and has 800 by 600 pixel resolution, which makes it more comparable to the other available Kindles. With a price between $130 and $135, It is also a tad more expensive than the Paperwhite or Nook Simple Touch with GlowLight, despite its lack of light.
All three of these competitors are similar in size and functionality to the various Amazon Kindle e-readers. They all let you sync with apps on other devices, and also all allow you to lend certain authorized books to other people with the same devices. They best the Kindle in one area: All these other e-readers come equipped with micro SD card slots to expand memory up to 32 GB.
The types of e-book formats that can be read on all the devices vary a bit, so you can't necessarily switch devices and move your content. All of the devices have access to sizeable libraries of e-books, although Amazon's library is currently the largest.
Another possibility is to eschew a dedicated e-reader altogether and use a multipurpose tablet, which is equally portable and can perform a host of other functions. They typically have back-lit color LCDs (liquid crystal displays), which would lend themselves better to textbook, cookbook, magazine and comic reading since those media generally include color images. Some choices are Google Nexus 7, iPad and Amazon's own Kindle Fire family of tablets. They can all be used to read e-books via e-reader apps, including the Kindle app. And the less expensive tablets are close to the price of the most expensive Kindle Paperwhite at this point.
One disadvantage of LCD tablets is that they do not have nearly the battery life of E Ink readers. They usually last only hours rather than days or weeks on one charge. They are also quite a bit heavier. Tablets also have greater problems with outdoor or other bright light visibility due to glare, but do not have two E Ink related issues: ghosting (faint leftover images of text from previous pages) and flashing (a brief flash that occurs as an E Ink screen resets). However, those E Ink issues do not render a page unreadable, and they are apparently less noticeable on the newer e-readers.
You can avoid an extra device purchase altogether and read Kindle and other e-books on your computer or your phone. Amazon has created free Kindle applications for pretty much all computing devices. And with Amazon's Cloud Reader, you can read your books through most Web browsers without any downloaded software. The Kindle itself is a bit of a loss leader, and Amazon actually makes its money from book sales rather than hardware sales.