The problem is, about 9 out of 10 of people who set out to write a novel don't actually finish, either due to time constraints or because it turns out to be a lot more work than they thought. Usually - and this happened to me - the words and sentences hitting the page don't match the lofty ideals in the mind, and it's all too discouraging. The trick is to plough on regardless, because good books come about through rewrites, editing and revision. They don't just pop out fully-formed.
Because so few ideas turn into finished books, publishers don't want to know about your plot outlines or your plans for a series of fifteen volumes. They want to see finished product. (And once they see it they turn around and reject 998 out of 1000 unsolicited submissions.)
If it's all so difficult, why do people bother?
Usually because they have a burning desire to write a book ... for example, their characters are living in their brain and won't stop bugging them, or the tale has to be told no matter what the sacrifice. Every time I considered quitting I'd picture Hal and Clunk fadng to black, unseen by anyone but me, and the thought of losing them forever was enough to get me going again. Usually with a severe reprimand from Clunk and a sarcastic comment about quitters from Hal.
Anyway, there's all this and a lot more in my articles on writing and publishing.
Hope that helps. I don't mean to sound discouraging but writing a novel is a huge challenge. It can be frustrating but it's also a massive rush when the first draft is done and you can start on the polishing and rewriting.
This is the text of my reply to an emailed query on writing a novel and getting published. I did give it a light edit before publishing it here ... force of habit.
Simon Haynes is the author of the Hal Spacejock and Hal Junior series (Amazon / Smashwords / other formats)