Whats the difference in audio book formats?

I want to pre-order the book Mistral’s kiss on unabridged audio cd but I’m not sure which format to buy. They have one with the bar code 1423322304 that says unabridged lib ed for .72, one with barcode 1423322290 unabridged edition for .71 and one with barcode 1423322312 mp3 cd unab mp3 edition for $ 16.47. They all say they are unabridged audio cd. Whats the diffrence?