The Crafty Art of Playmaking by Alan Ayckbourn
A book of two halves, covering the writing and directing of plays, by a master of the craft. Alan Ayckbourn has written a vast number of plays, and directed many of them himself at the Stephen Joseph theatre, Scarborough.
I got this book out of the library after I'd been to a scriptwriting workshop recently, and I would recommend the first half to anyone interested in writing plays. Although Ayckbourn is concentrating on stage plays, most of the advice carries over to other types of script such as a radio play. There are 39 highlighted snippets under the heading Obvious Rule Number x, scattered throughout the Writing half. Some of them are not so obvious, and you may have reason to thank him for pointing them out.
He uses examples from his own plays, which makes sense as he knows them well and also knows the processes behind them, and the mechanics of putting them together. I would say it helps to have a passing familiarity with at least a few of his plays as it may help put some of the examples into a wider context; it's probably best not to read this if you may be upset at finding out the ending to a play you haven't seen/heard/read yet.
I admit I didn't read all of the Directing half of the book, but I do think if I was at the point where I'd written a play that was likely to be staged, it would probably be useful. Some of it handles the technical side of being a director and might only be of interest to those who'll use that knowledge, but mainly it gives an insight from the other end if you like. A key moment of understanding came, for me, when he talks about the director cutting the play - he also said that a script isn't literature, it's a blueprint for how actors will behave on stage. In other words, stop agonising over perfection as it may not stay that way anyway.
Outside of the writers of scripts, this book would also be of interest to those who are interested in theatre or keen on Ayckbourn. While it's by no means an autobiography, it does include anecdotes from his long career, insight into his way of working, and the background to some of his works.