First of all, what this book is not: this book is not voyeurism, if that's what you're looking for, look elsewhere. So what is this book? This book is an examination of human nature. But it's not a dry, pedantic examination, it's a look at human nature in all of its beauty and all of its unseemliness. The lust, the love, the suffering, the solitude is all in that room into which Henri Barbusse has allowed us to look. Barbusse shows us that we live in a world of pretension, a world in which we all strive to create a superficial image, a plastic persona, in order to impress our fellow human beings, a world of ego and lies.
The protagonist of this novel finds a hole in the wall above a blocked off doorway in his hotel room, a hole which allows him to observe the occupants of the other room without their knowledge. What he sees - birth, death, young love, forbidden love, adultery - shows him what human nature is without the affectations of society. What he sees is Humanity stripped bare. He'll never see society the same way again and neither will you after reading this book. Forget about going down the rabbit hole, just take a peak through Barbusse's hole in the wall.