First of all, there are different types of scripts. Submission or “spec” scripts are bare bones scripts with minimal scene direction and no camera instructions. There are a variety of other stages though–where the director, producers, alternate screenwriters, the studio head’s daughter all get to add modifications and instructions–which a script goes through before it is a shooting or production script. This is the “final” version of the script, which is then generally edited, annotated, marked up, stained, burned, sat on, used as an umbrella, tossed in the back of the equipment van under all of the still-hot arc lights, and generally ignored. What comes out on film may or may not have a passing resemblence to the “final” script, depending on how much star power the leads have and how cowed/exhausted/hung over/drugged out the director may be.
Spec scripts are a dime a dozen; I’ve seen Hollywood bookstores setting them out at an armful for $1.00 (mostly crap). I suppose agents, directors, and producers are as innudated by these as publishers are of manuscripts. Shootings scripts are rarer, as directors and producers often take some effort to prevent their leakage to the general public (coding scripts, only handing out certain pages or letting actors have only their own dialog.) The redlined shooting script–the document that is supposed to include all final, nonimprovised script changes–is usually held as property of the studio or filming company and isn’t for sale, per se.
The published “scripts” you buy bound at the bookstore or on Amazon.com aren’t properly scripts at all; that is, they often do not conform to standard screenplay format[sup]*[/sup] and generally include all sorts of ancillary information that would never be included in a script. (See The Complete Guide to Standard Script Formats: The Screenplay for information on script format.) Scripts delivered to the production team and actors are often accompanied by production information, shooting directions, character biographies, backstory treatments, et cetera but these are not part of the script proper.
I bought the “screenplay” book for Eternal Sunshine of the Spotless Mind recently (Charlie Kaufman’s screenplays are actually pretty enjoyable to read in their own right, unlike many scripts), and I note that it includes several scenes that are either out of final editing order or are cut (like the Velveteen Rabbit), while missing some of the improvised scenes (the circus parade) that were not in the shooting script. The screenplay is bookended by an incomprehensible introduction written by Michel Gondry and a Q&A transcript with Gondry and Kaufman in the end, which itself is nearly worth the price of the book. There are earlier working scripts available online, however, that are interesting as an examination of how stories change from the writer’s concept to production, and this is well worth checking out as well.
Stranger
*They’re often printed in what is called Published Play Format (by Acting Edition) which compactifies the dialog and stage direction and removes camera and editing instructions.