It's actually not that obscure to people interested in French19th century lit (the sort of people who read Balzac or the romantics) and neither to Poles, but IIRC the introduction of my edition mentions how it's been oddly (for a major and rather unique work) ignored until the late 20th cent. in several major languages, notably English.

It's certainly worth reading, a real oddball mxing together so many genres that book. It's pretty much a good thing that you didn't buy it. The only complete, reconstituted edition is fairly recent (Flammarion for the paperback, something like 2010 or 2009). Previous French editions were for sizeable portions that had been lost a translation back in French of the Polish translation. That was the version I read long ago, the real French original (recreated from two editions that the publisher tracked down among collectors) is much better/cohesive. There's also two versions of that book published, an earlier one and the last revision by the author which is somewhat darker and better, IMO. The two versions have now been reconstituted properly, previously the French text mixed elements from the two versions.