What is the author's style in Migraine by Oliver Sacks?

The book is designed strictly as an informational source with the reader left to use the information as he or she sees fit. There are great details given with regard to physiological and psychological impacts of migraines. While Sacks doesn't offer a base reason for all migraines, he does describe an array of migraines by type and presents details gleaned from his observation of many migraine patients. This information is often presented as case studies. There are literally dozens of these included in the book and only a fraction are presented in this summary. The case studies are identified only by number and details of the case, including age, gender and other basic information about the patient. Names are omitted.