Sacks owes his popularity to his ability of telling cases of patients with spirit and kindness, crafting little stories out of each. What is important in every depiction is not much the details, as the overall truth and the perspective adopted.
He Sacks has compiled a massive book (this is the updated and expanded version) about case stories of people affected by neural disturbs that prevent them from a normal musical experience. This is admittedly one of his passion, and in principle an interesting topic for a book a la Sacks. But once you start reading, boredom comes quickly, the text does not flow, and such abundance of cases is just redundant, and there is little of the aforementioned qualities of Sacks' narration in action. So it overall ends up by annoying, when not speaking of trivial things (like people who ear music in their heads that they never heard: come on, every composer does it, it's just automatic when you start composing music, and I don't think composers are more sick than normal people!).
Overall, quite boring and disappointing.