The BBC did six Philip Marlowe stories from 1977 to 1988. They are all very well done, and every time I hear the opening theme music, I feel like I'm being delivered straight to early-mid-20th Century California, land of noir corruption. Chandler's dialogue is often used in these productions, so the style of the books carries over very well to audio drama. Even if you already know the stories from the books or movies, you should be able to enjoy this medium equally well.
My reason for taking one star off my rating is the choice of Ed Bishop to play Marlowe. My understanding is that Bishop was an American actor who lived and worked in the UK. As such, he was probably chosen more for his availability then his suitability to play Marlowe in audio format. We all have expectations for who should play a well-defined role like Marlowe, particularly when they have been played successfully in the past. In this case, I'm thinking not just of the actors who have played Marlowe on the screen, but Gerald Mohr, who was Marlowe in the post-war radio series over many episodes. I try to put aside the familiar actor when I experience a new version of an old favorite, but I'm afraid that Bishop just doesn't ring true in this role. He's obviously a competent actor, but somehow his voice just doesn't match up well with Chandler's dialogue and narration, particularly when wisecracking or cynicism is called for. When I hear Bishop, I think more of the old Hollywood newspaper reporter of the 1930s-40s than a private eye. There's just not enough man's man in his voice to carry off the role seamlessly.
That being said, I still gave these recording four stars, and I still recommend them. I've listened to all the stories twice now, and when I've let them rest long enough, I'll go back to them again.