Mainly, I tried to focus on the areas not covered by all the other books.
And very few of them get into more than one area of scripting.
As for radio...I did include the revised chapter on radio drama, with the
proviso that the field itself is shrinking still, except for occasional
big projects which are off-limits to freelancers. The main growth area, I
think, will be in audio books, which are getting more and more to sound
like radio dramas.