This book is not what I thought it would be. It is mostly a period piece discussing French writers, playwrights, poets, and intellectuals, i.e. not my cup of tea. Opium is definitely not the main topic of the book. While some parts have extremely worthwhile tidbits about opium culture and Cocteau's views and experiences with opium and withdrawal, for me they did not justify reading the entire book. Readers be warned, this piece is probably only worth reading for those interested in early 20th century French literature. I haven't read De Quincey's Confessions of an English Opium Eater, but I imagine it is head and shoulder's above this text if the reader's primary interest is in the drug, as mine is.
If one were to read this book for its account of opium use, culture, and withdrawal, my recommendation would be to put it down around page 100. The good parts are almost entirely in the first half, the second half is practically irrelevant.
I will grant to Cocteau that his descriptions of opium smoking are wonderfully vivid, they're really the only reason that this book was any pleasure to read.