In years past, electronic books were esoteric gadgets that catered to an elite crowd. But now the product has gone mainstream. We’ve rounded up the top e-book readers in the current market. You can further compare reviews at http://reviews.cnet.com/e-book-readers.

Cool-er e-book reader

CNET rating: 3 stars out of 5 (Good)

The good: Lightweight; eight color choices; 1GB of internal memory with an SD card expansion slot that allows up to 4GB of additional memory; battery’s removable and replaceable; accepts JPEG, PDF, EPUB, TXT, and MP3 file formats.

The bad: Feels a bit like a “budget” e-reader; drag-and-drop e-book loading less convenient than Kindle’s; buttons are stiff and aren’t intuitively labeled; interface lacks polish; navigation a bit cumbersome; slow screen refresh when flipping pages; nonstandard 2.5mm headphone jack.

The cost: $250.00

The bottom line: Has some nice pluses and costs $110 less than the Kindle, but not as big a bargain as we had hoped.

Sony Reader Digital PRS-700BC

CNET rating: 3 stars out of 5 (Good)

The good: The PRS-700 is sleeker than the Kindle; faster processor speeds up the device; new touch-screen interface offers better ergonomics; with the addition of an optional memory card (SD or Memory Stick Pro), it’s capable of storing thousands of electronic books; font size is adjustable; displays Word and PDF files (and zooms them), shows most image files, and plays MP3 and AAC audio; built-in LED lighting isn’t great but allows you to read in the dark.

The bad: New touch screen is more glare-prone and doesn’t have as much contrast as Amazon’s Kindle or Sony’s PRS-505; built-in lighting is from the screen periphery, not backlighting; eBook Library software isn’t available for Mac owners; no support for Audible audio books; no built-in wireless access.

The cost: $349.99

The bottom line: The PRS-700 takes one step forward for Sony digital readers–and a couple leaps back.

Amazon Kindle 2

CNET rating: 4 stars out of 5 (Excellent)

The good: Slimmer and sleeker looking than the original Kindle; large library of tens of thousands of e-books, newspapers, magazines, and blogs; built-in free wireless “Whispernet” data network — no PC needed; built-in keyboard for notes and navigation; a faster processor speeds up the device; with 2GB of internal memory, it’s capable of storing 1,500 electronic books; font size is adjustable; displays image files and plays MP3 and AAC audio; compatible with Windows and Mac; Text-to-Speech feature.

The bad: No expansion slot for adding memory or accessing files; files such as PDFs and Word documents aren’t natively supported, and need to be converted at 10 cents a pop by Amazon; battery isn’t removable; hardware and content still too expensive.

The cost: $359.00

The bottom line: While it’s still short of perfection — and is too expensive — it offers a range of improvements that makes it the best overall e-book reader we’ve seen.

Amazon Kindle DX

CNET rating: 3.5 stars out of 5 (Very Good)

The good: The Kindle DX offers 2.5 times the screen real estate as the Kindle 2; native PDF support; you can switch from portrait to landscape mode by just turning the device; large library of tens of thousands of e-books, newspapers, magazines, and blogs; built-in free wireless “Whispernet” data network — no PC needed; built-in keyboard for notes; faster processor speeds up the device; with 4GB (3.3 usable) of internal memory, it’s capable of storing 3,500 electronic books; font size is adjustable; decent battery life; displays image files, and plays MP3 and AAC audio.

The bad: Expensive; somewhat heavy compared with Kindle 2; no expansion slot for adding memory; battery isn’t removable.

The cost: $489.00

The bottom line: The pricey Kindle DX offers improvements over Kindle 2, but its larger chassis has its pluses and minuses.