Flash Players
Pros: Very portable and light; less susceptible to damage from drops
Cons: More expensive on a per-gigabyte basis; limited capacity

Hard Drive Players
Pros: Very large capacity; large screens for video playback
Cons: Internal hard drive makes them fragile

Important Features:
Capacity: For audio books, minimum capacity requirement is 2 GB as an unabridged audio book is 700MB to 1 GB.
Format Support: All players support MP3, but fewer play back AAC, OGG, WMA, and other formats. Moreover, many DRM-protected files can only be transferred to certified compatible players.
Video Features: For video players, screen size is critical for a quality viewing experience, though you can output video to a larger screen with the right accessories.
Book marking feature: Look for book marking feature in mp3 players as audio book recording range from 6 to 16 hours and you want to pause and listen to the audio book from where you stopped. Most of the iPod Mp3 players have this feature and some of the Creative Zen players like the Creative Zen Vision:M

Consumer Reports Top Ranked Flash Players:

1. iRiver Clix (4 GB) Digital Media Player
2. Samsung YP-T9JAB
3. HyunWon MobiBLU B153
4. Apple iPod Nano 8GB
5. Cowon iAUDIO T2

Consumers Report Top Ranked Hard Disk Players:

1. Apple iPod Video (80GB)
2. Apple iPod (30GB)
3. Creative Zen Sleek Photo (20GB )
4. Creative Zen Vision M (60 GB)
5. Toshiba Gigabeat MEV30K Digital Media Player

Try your favorite before taking it home. We can't stress this enough. Make sure you can use the on-screen display to navigate to a specific song, and ask a clerk to show you how to transfer music to the device, if possible. Always bring your own set of headphones to listen to the sound quality of each unit you're interested in.