Orson Welles Mercury Theater is probably one of the most important OTR series ever produced. Although most notable for its infamous War of the Worlds broadcast, each and every episode in the series is fantastic storytelling for the Audio Medium.
This collection from RadioArchives is probably the only release I've ever seen that collects these great episodes and the quality is outstanding. Dracula in particular (my personal favorite for years) sounds better here than I have ever heard it and I doubt it will ever sound any better. The quality of the restoration is as amazing as the quality of the show itself.