This is regarded as the great work of Belgian fantasy (at least in the novel form: there are loads of Belgian comics and films with sfnal content). It's quite difficult to get hold of and I eventually picked up a copy of the 1998 Atlas Press translation on eBay. It appears at first to be about the peculiar inhabitants of the house of Malpertuis, in a city which is presumably Ghent in the dying days of Francophone supremacy; but in fact it turns into a peculiar confrontation between the organised Catholic church and the gods of ancient Greece. My edition makes the inevitable link with H.P. Lovecraft; I would add James Stephens' The Crock of Gold as a potential source, and I wonder if Neil Gaiman drew on it, consciously or not, for American Gods (and likewise, for the nested narrative structure, David Mitchell for Cloud Atlas). Ray is not quite as terrifying as Lovecraft (though fairly gruesome in places), and he is certainly not as cheerful as Stephens, but he does add a certain level of surrealist incomprehensibility to the mix that is appropriate for a slightly older contemporary of Magritte, who like Magritte stayed in Belgium and wrote this book during the German occupation. Certainly an essential read for sf fans interested in Belgium, or Belgians interested in literary sf.
cassave is one of several people who have recently shifted completely from Livejournal to Facebook, but now I know where he got his name from while he was here.