Blinding Light by Paul Theroux
Slade Steadman is the author of a world-famous travel book, but has struggled to match its success for the past thirty years. A journey downriver in a remote eastern province of Ecuador gives him the experience he has been seeking and a miracle drug, which induces temporary blindness. On his return to the USA, Steadman is rejuvenated able not only to write and remember, but granted an almost uncanny prescience, bordering on second sight.