shelves of the trade
I think The Singing Detective was the first screenplay I actively sought out and bought. It was probably a bad example in some ways, for brilliant though the TV series is, Dennis Potter wasn't exactly skimpy with his stage directions. He was directing from the page, a habit I can still sometimes fall into.
Then there was Tarantino. In my twenties I reread the scripts for Reservoir Dogs and Pulp Fiction over and over. By the time I decided to try my hand at stand up I was already starting to amass a small collection of scripts and 'industry insider' books. I continued the practice for comedy and began buying up 'how to' books for jokes and stand up. I now have five shelves worth which I broadly think of as 'industry', covering everything from stand-up autobiographies, interviews with creatives to straight joke books and screenplay formulas. I've taken photos of them above for you lovely people. Now run out, read them all and you'll be just like me.