Victor Hugo's novel Les Miserables was adapted to radio in 1937 in a format similar to how television would later create it's own prestigious mini-series adaptations. It aired on Mutual from July 23-September 3, 1937. Starring as the novel's hero Jean Valjean (and as the book's narrator) was Orson Welles, buttressed by Martin Gabel, Agnes Moorehead, Bill Johnstone, Everett Sloane, Frank Readick, Gwen Davies, Ray Collins and Alice Frost. It was during this time that Welles and most of the performers appearing with him founded the Mercury Theatre, which would make its true radio debut the following year with CBS' Mercury Theatre on the Air.
Listening to Les Miserables, it is very much in the same spirit as the subsequent Mercury Theatre on the Air - in part because Welles seems to have bit off a little more than he could chew. It's well-documented that Welles kicked off the Mercury Theatre on the Air by trying to quickly pare down Bram Stoker's Dracula into a viable hour-long drama and it was a struggle for his staff to assemble it in time. Similarly, it feels as though when he started Les Miserables's first episode he didn't have a final script for the series. The first five episodes go fairly briskly through Hugo's novel, but in the 6th episode the story jumps far ahead to the story of Jean Valjean entering the barricade to rescue Marius - whose entire romance with Cosette happened in-between episodes. Then the 7th episode is mostly a recap of the previous episodes, until finally adding Valjean's death from the novel.
But although the pace of the adaptation is uneven, it's a very well-produced program with terrific performances by Welles' regulars. I first heard this series before I had read the novel or seen any of the film adaptations - I came away feeling I had a decent grasp of what the novel's plot and themes were. I also think the 5th episode with the account of Valjean being buried alive is a piece of excellent radio, a very well-done bit of thriller melodrama.
You can hear all seven episodes of Les Miserables on this YouTube playlist.