One of Julian's (from the old Screenwriter magazine) regular ideas is that storytellers are paramount - and that screenwriters can/should/might consider writing novels instead. There's two parts to his idea:
1) Storytelling is a separable thing - you can define a storyteller as something separate from a screenwriter or novelist. And following this that screenwriters and novelists are types of storyteller: Species - storyteller, genus - novelist.
2) Commercial reality - the odds are better on novels.
I'm only going to talk about the first point - Julian is an agent, so we must defer completely to his knowledge on the second!
I have great difficulty with this idea - I just don't believe there is enough equivalence between being a dramatist and a novelist to make a casual switch between the two. To say that they both 'tell stories' is only true up to a point, and here's a few reasons why...
Story, Fabula, ‘sujet’ a little narratology with your afternoon tea
It will help if we take a second to tease out what is going on between the idea of the story and the telling of the story...
Fabula (fable) is a story at it's most basic; the underlying pattern of a events without any 'art'. If a story form (as per Booker) can be expressed as 'Overcoming the monster' then a Fabula might consist of a series of events in which a knight slays a dragon to capture a princess. Or it might be that a Policeman takes anew job at a seaside town and must defeat a shark to prove that he's still 'got it'. 'Sujet' is just a fancy term for the employment of narrative on that series of events - the 'telling' of the Fabula.
To simplify we might say that there are story events (plot) which are then 'told' by the writer in a narrative.
So it looks like we could quite easily just decide at the last minute, having planned our Fabula, what our 'telling' will be. That is we proceed in one nice long neat line down a logical path from Story Form to Fabula to Narrative, each a more specific, evolved, version of the last. And when we get to the telling we could decide to make this story a novel, a play or a movie.
The big difficulty with this is that Fiction and Drama operate in two places in this process. Fiction writers write the story as it is read, they tell the story. But dramatists tell the story to a set of people who then tell the story again. Fiction is the product while drama is a blueprint. This means that drama (and I mean Theatre, TV, film radio) gets a whole layer of technical understanding that fiction does not. This must be learnt, not only as a technical exercise but as a core understanding of the medium. This takes time and experience. Acquiring the art of writing for theatre after writing for film for instance could be massively confusing, just as the leap from theatre to film takes quite a lot of effort to make - though this jump is much closer that leaping from film to fiction...
Many a novelist has fallen foul of the desire to write a play and ends up with a 'speechy' mess that has no underlying drama in it - that is the novelist is expecting the audience to *read the characters words and infer action*. Dramatists who start writing often find they have very short chapters that seem perhaps prosaic, with underdeveloped characters - they are expecting the reader to *infer character from action on the page*. These 'errors' are not because either type of writer is stupid or bad, it's because they have sent years (decades) perfecting their craft in one mode or the other.
Writing fiction is writing the final product - the audience reads what the writer writes, it's a direct relationship. In theatre what is written is not the final product it's 'only' the score, it's what gets performed. So in fiction the text is 'inhaled' by the audience and in drama the score is 'exhaled' to the audience. In this the dramatist is closer to the composer of music than to the Novelist.
Film is somewhere between; the writer is writing more directly, allowing some colour into the prose as a way of capturing their audience (the script reader, producer and director), but most of the written text is still a score - for the actors, camera, director and editor to 'exhale'.
To switch from one to the other is not much shy in understanding and effort as that of moving from musical composition to writing fiction. And there's a reason that writers chose one modal form over the other - they are better at it, perhaps they are most inspired by it, they prefer it. It's not trivial to ask someone to move from one to the other.
Interlude: Practicalities of time
At the very least there's a massive learning curve involved in this switch. If it takes lets say 3-7 features to 'make' a dramatist, then how many novels does it take to make a novelist? 2-3? At something like 1-5 years for a novel does that mean it's going to take our dramatist 2-15 years to figure out how to make the modal switch. That's a lot of time to NOT be writing in the most connected and powerful way you can...
Having watched friends become playwrights OR novelists there is a bit of creative jostling early on but people largely settle on one or the other and sink themselves into it. The exceptions, the people who pursue both long fiction and full length plays/movies, run around 10%. And they will be better at one of the modes. Thinking of the big hitters who did both in the 20th century; Camus, Beckett... Beckett perhaps is the only one who was good enough to make formal innovations in both modes (though they were much clearer in theatre). I am sure there are plenty of people who do both - feel free to add them in the comments - but the majority of us are not prepared to take that much time out of our good writing to be beginner and learn all over again in the other mode.
So there's a question for Julian in this - I am not sure he can answer it - but is it worth taking lets say 5-10 years out of your screenwriting career to become a novelist? Is it worth even 5 years of uncertainty and lost time to make the switch?
Question: How much attention do Novelists pay to Aristotle's Poetics?
Aristotle's insights are for dramatists. As dramatists we are used to thinking in terms that can be (at least partially addressed) by the Poetics. In the Poetics there is a particular slant on action, choice and character. Aristotle talks about the scope of drama (or how big it is, how long it should take) and he *deeply* prefer plots over texture (the analogy being that drama has the neatness of a line drawing not the messy nothingness of applied colour).
Novelists just don't need this kind of thought. Novelists have been crafting stories which make no 'dramatic' sense for a very long time, they are able to proceed using the messy applied colour of pure characterisation, or theme or setting. To a certain extent fiction is 'post-dramatic', it does not need to rely on dramatic structure to tell stories - fiction writers don't need to tell the story of the fable through dramatic means.
Perhaps we are confusing story tellers with dramatists - in fact they are nothing like the same. 'The Drama' is a specific set of strategies and 'rules' with which a story may be told. The current epitome of the drama is the Hollywood Three-Act structure, the 'Grand Argument' screenplay.
I am certainly NOT saying that dramatists shouldn't write fiction. What I am trying to get my head around is why the jump is difficult - at least more difficult than Julian implies. The positive side of all that is that if you are going to jump it helps to know why it feels so different. And I really hope for you that 'difficult' can just mean 'awesomely fun and entertaining'.
Personally writing fiction pretty much feels like crawling through glass where drama is like flying. And believe me I have tried - and will probably try again - to write fiction. My intense background in theatre means that Theatres highly artificial and codified mode feels like second nature to me, but it was the 'thrill of the novel', those penguin modern classics that I used to buy for a dollar ar Silvios books in Cuba St, that set me on the long journey of being a writer... Reading my way through the modern Europeans as a teenager in far off NZ literally changed my life. I hope that my writing could do that one day too...