I first fell in love with h2g2 through the books, then the movie, and finally these radio scripts--I'm too young to have ever heard the original radio series. I tried listening to the BBC "Quaternary" phase, but it just wasn't the same.
Reading the scripts can never fully approximate the feeling of a radio show, of course. From what I've read of it, the entire affair was zany. At times, apparently, the end of the episode wasn't even written before they began recording the beginning. This sort of thing is precisely the real-life craziness from which something like h2g2 can emerge and feel so appropriate.
Still, it was cool to read the radio scripts and see how the show differed from the books. The books will always be my favourite, partly because I am primarily a novel person, and partly because I read them first.