If I were thinking about writing a novel then, regardless of the setting or genre, I would need to find satisfactory answers to two questions:
1) _Whose_ story am I going to tell? The main character or characters need to be clear and interesting from the outset. It will be their story, after all, that keeps the reader engaged.
2) What are the central themes to be? I don't mean the story or plot details here - I mean the 'message' the book is trying to convey. From the schedule you have on your website, you allow yourself 6 months from starting work on a novel to having a first draft, then a month for each of two edits and another month for a final version: you need to believe for those 9 months (preferably longer) that you're spending your time on a book that _needs_ to be written, that has something important to communicate and which also provides the reader with their motivation for buying it.
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If you plan to use pre-existing characters in the current ED timeline, then you need to ask yourself who stands out and who appeals to you to write about. I'm wary of suggesting anything but I will say that very few characters have really 'come alive' for me as a result of the Galnet posts. The closest would probably be Elaine Boyd, the investigative journalist looking into some of the puzzles in the first year before she was killed (a mystery that is still ongoing) and Ishmael Palin, who seems to have a knack for hitting barriers in his research and somehow getting over them (OK, he's been dependent upon members of the Elite Federation of Pilots bailing him out and providing him with materials and funding).
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In terms of themes, I will only say that this is something that any author must always decide for themselves! You're the one who will need to motivate yourself, so all you can do is write from the heart on a theme that really matters to you.
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In terms of a general story, there are two areas that I would like to learn more about and I am taking/have taken steps to try and make discoveries in-game, e.g. by looking for signs of signal sources near the borders of permit-locked regions. The first, which is probably the most difficult to write about in the context of a novel, is the history of spacefaring civilisations in the Milky Way: are we one of the first or have there been tens/hundreds/thousands during the Milky Way's lifetime and where are they now; how did/do they interact with each other; how many are active and how many are dormant or deceased? The other, easier, aspect I am keen to learn more about is the development of sentient AI: how it first appeared; what people's responses to the creation of AI were and how did the AI itself perceive the purpose of its existence and how did it want to interact with the human race? There are some lessons here that are relevant to our own society in terms of the tolerance of strangers and the fear and wonder of new technology: we may be only decades away from this achievement in real life and how would we react?
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Whilst I am glad that you are thinking about writing another Elite novel, the process of buying a license and paying to write, as opposed to being paid to write, is worrying: authors are often very badly paid for their work as it is and I would very much like for them to be able to afford to eat and live well (compare the average earnings of published novelists, who may be the sole author of their work, with that of junior programmers working in the computer games industry, in teams of dozens or more). I hope that whatever you decide to write, you are able to make it a success!