Hi DG,
I started in screenwriting, have a number of shorts made and one feature. Everything above is correct, and if you want to look up Max Landis on youtube - he has some very passionate videos on there on how the hollywood machine works from the inside perspective. He's a little crazy but grew up inside of Hollywood, and from a constructive stand point he knows the screenwriting business inside and out.
I've written a number of feature scripts, but as mentioned only one of them has been made into a film. It's not that they're bad, I've gotten so far with them in competitions and for the biggest draw back I found was that I was an original IP. Because of this, the story is an unknown and much harder to get any investment for because making a film is a gamble. The common feedback I had was that, 'if only this was already a successful book'. I've not converted books into screenplays, but I have converted two screenplays into books.
There was a point in the mid-seventies when the studios were going bankrupt because they were churning out the same thing they had for the past twenty or so years. There's a documentary called easy riders, raging bulls which showed how Dennis Hopper, Francis Ford Coppola and the likes managed to get into the system. Those doors were quickly closed. Most screenplays even when green lit don't get made, there's a black list made up every year of the best scripts not made.
The studio system has a formula and it sticks to it. That's exactly why there are so many sequels and copy cats. Studios also have preferred spec writers. These are the guys who get the call, "Hunger Games was a success, I've just bought the option on Maze Runner and I want the script by..." This is how they work.
There are always exceptions to the rule, but don't kid yourself into believing that this isn't the rule. Unless it's an original story about animals or Christmas (or animals at Christmas), you've an uphill battle. The most money grossing in the film industry is found not by the tent pole movies, they make their money off merchandise. The ones that make the money are those unknown names you scroll past on Netflix, the ones in-between the films you've seen.
However - you want to adapt your book into a screenplay. You've already got numbers you can show them. They will know better than you, and they won't take chances. Even if you have a director on board with you, they have to be strong enough to be able to have final cut of the film. Something the studios rarely give up, more now than ever.
Screenwriting is the art of the empty page. Paragraphs need to be two or three lines at the most. Dialogue punchy. Screenplays are generally 90 - 120 pages long. This is because each page is equal to one minute of screen time. The equation is slightly different for television, but it's a good rule of thumb and screenwriting software like final cut or the free one Cetlx will set the pages out to match regardless.
The first ten minutes is your inciting incident. Then twenty pages of set up and introducing your main characters. Thirty pages in and you have to have your first twist. Into the second act, all the trouble piling on until page 60 (for a 90 minute film) or page 90 (for a 120 minute film). The second act must end with the protagonist at her worst and realise what must be done to conclude the story in the last thirty pages. To break these rules you have to be recognised or have a superb story. There's no room for fat what so ever. Aaron Sorkin's script for Social Network came in over 300 pages, but it's all dialogue and everyone speaks really fast.
There's also a ruling on how many scenes you should have per act. Best practice is 14 index cards per 30 pages. It prevents you from staying in one scene too long.
This is where studios and authors don't get along and why they try to cut them out of the process. They want to stick to that formula no matter what. It's also why half the book is normally left out, because there's no room for it. Film isn't one persons vision, I believe Anne Rice wrote the screenplay for Interview - at least one version of it. Suzanne Collins wrote the script for Hunger Games so there's hope.
Another little bit on optioning, if the studio already has something in mind similar to your book. They'll option it and shelve it to prevent any competition. So if you are going to do this, make sure you read the contract thoroughly. Make sure there's a clause in there that the rights fall back to you if the film isn't made within X amount of time.
Something a little different:
Save the Cat! by Blake Snyder is a tongue in cheek look at the screen writing process.
Syd Field has a number of books and is regarded as the main man.
On Directing Film by David Mamet has volumes to speak on how films are put together.
I'm more than happy to go through more of the technical side but also don't want to teach you on sucking eggs as clearly you know how to write.
Bafta did a series called Guru which interviewed screenwriters which is also very good.
If you want to spend a little cash, Aaron Sorkin has a Master Class. It's a good foundation and covers television as well as film. I didn't learn anything from it, but found it entertaining at least. Plus - I'm a huge fan.
Most screenplays can be downloaded for free as a pdf - do what you do with books. Read the ones you like and watch the films, find the beats. oh - (BEAT) is used to convey a pause in a sentence. Shane Black, Quentin Tarantino, Woody Allen, Charlie Kaufman, Aaron Sorkin, William Godlman, The Nolan Brothers, David Mament, Lawrence Kasdan, Nora Ephron, David Goyer (check out his youtube interviews for a good understanding on how the industry works) are all good reads.
RX-79G mentioned the 400 page mini series screenplay. Completely right - no one will read that, they only want to see the first episode and treatments (one pagers) on the following episodes. This goes for the longer shows too - traditionally they'll make a pilot before signing off on the rest of the work so there is no point writing the whole thing.
I'll finish with saying that it is a different beast, but I for one love writing them. And if you do want to go down that path, I'd be more than happy to answer any questions or spring board some ideas. If I may be so bold as to suggest writing one from scratch first, just to learn the beats. Even if it's a crappy b movie.
More importantly, good luck! It's an awesome experience, one I will be doing again soon.
