This manga is really entertaining, an epic tales of heroes fighting great evil.
It's a prequel to the Lodoss War series that tell the simple story of demons invading the land, they must be stopped by a party of adventurer. It of course introduce character and set up event that will more or less be relevant in the main series but can totally be read on it's own.
What really stand out is the art, it's drawn by the guy who also do the illustration for the novel of the main series and so his art is really fit for cool looking one page illustration, for a
manga ? it's complicated.
I'm no expert but i would describe it as harder to read than other manga, you have to take a few second very often to look at a panel to fully get what's going on it, so it break the flow of your reading, also there is a lot of text at what feel like random place and you're often confused what bubble you're supposed to read first.
All that to say that it's harder to read than your usual manga but this dark art is outstanding and each panel could be a wallpaper.
The story is very simple, the lodoss series are all about classic fantasy story, this one may feel darker because of the art that make everything more serious and mature than in any other installment of the series, but it's still a story of good vs evil.
So yeah a good read for fan of the series, fan of fantasy story and fan of crazy good looking manga.