I don't think the 2006 radio came with an auxiliary jack. A way around the cd skip problem may be to buy a new radio that does have and aux jack, or see if one can be added to yours, then you could connect the headphone jack from your phone to there and listen to audiobooks played from your phone. I listen to audiobooks frequently and using the phone lets me continue listening to the same book in a different vehicle, mowing the lawn, etc. What I've done for my 2008 is buy a
12v to USB adapter to plug into the dash, and a
Bluetooth receiver to plug into that. Plug the audio jack from the Bluetooth into the truck's radio, pair the Bluetooth and keep the phone in my pocket. I suppose even better is a radio with Bluetooth...
Of course, if your books are only available on CD transferring to the phone could be a pain.