Michael Chorost's Rebuilt (2005).

Tells of regaining hearing via cochlear implant - 16 pins that feed impulses into Chorost's neurons near the ear.  Those of us with organic hearing are using a bunch of tiny hairs to pick up sound waves, and we likely don't think too much about how it all works, or whether we are really getting a 'realistic' sonic landscape.  But Michael Chorost suddenly lost his hearing in 2001, and chose to get the surgery to have an implant placed in his head, and Rebuilt tells the story in a compelling fashion by mixing the science, his experience of hearing, the concept of the cyborg, and his thoughts on communicating and connecting with other people.

While I've read a number of things that describe the neuroscience of vision in some detail, this was the first book I've found that does something similar for the auditory sense.  The full rig that makes the implant useful includes a microphone, a processor that can run software to scan the sound and adjust/filter the input to create output for the 16 pins, and a radio relay unit that is magnetically linked to the implant on the outside of the skin on the skull.  Many rounds of mapping are performed to fine tune the processing to the specifics of the way the pins transmit data into the brain, and new software in the processor can make improvements by (for example) increasing the transmission rate.

One of the stories that really brought the whole concept home for me was telling of hooking up the rig to a CD player, such that no sound waves were produced, simply electronic patterns, which were transmitted to the implant and created the experience of hearing for Chorost.  Just as our vision is a creation of the brain, so too our auditory sense.  And it's quite interesting to track how his hearing ability improves over time, both due to software enhancement and neuro-plasticity of the brain.

Chorost mulls over the concept of the cyborg quite extensively through the book, contrasting this concept of the technologically enhanced human with the quite different notion of a robot.  Knowing that your hearing is dependent on the hardware and software running on various gizmos will do that to a person.  He stresses the point that his implant does not improve on healthy human hearing, and takes issue with some of the more extravagant claims of Kevin Warwick (who wrote in I, Cyborg, "We will interface with machines through thought signals.")  We don't really have any clue yet how thoughts might be represented as an interface to the brain - in this situation what's being transmitted are representations of sound, not thought!