I’m writing a book and these first 20 pages are mostly just action so my question is if a book is like mad max fury road, (almost nothing but action) will it be annoying or not be exciting anymore after awhile?
Long fighting scenes are most of the time boring.
There I said it... I know it is primarily opinion based but there is good reason to say this. Part of it is because your story needs to be moving forward and a (too) long fighting scene prevents this from happening most of the time.
When I am reading the first pages of a story I first need a proper introduction to maincast of the story. This can be done with an action scene but if his motivation is not clear. I might not be so interested in his story. This could cause me to stop reading the story all together.
Another problem of an all action start is that I, as reader, will expect a climax that will top this start. You are making a promise of a lot more action in the story and when the story ends up to be a romance of some sort. I will be severely disappointed. This might cause me to stop reader anything you write in the future. So breaking that trust is not advisable.
So can a book with a lot of action be annoying? Yes.
It can also be very good. It will depend on how you introduce your characters. Make their motivation interesting and make good to the promises you set.
If you give the audience action, you've got to give some reason to care for that action. I wouldn't want to be reading about a whole lot of violence between some people I know nothing about - I'd have no stake in that violence, no one to root for. I wouldn't be particularly interested to find out whether this guy or that guy survives (or whatever the stakes for the characters are).
The reason readers care about anything you write about is the characters. We're persons, we care about other persons. (I use the word 'person' here to encompass characters who are not necessarily humanoid.) So, right from the start, you've got to give us characters. Show us who we should care for, and what their stake is in the fight. Tell us, at least to an extent, who's fighting who, why, what's going on. Show us the characters' human reactions, give us the interactions that help us connect to the characters. Give us a reason to care which way the fight goes.
And when I say "show us who we should care for", I don't just mean "introduce us to the MC". I mean give us a reason to care for the MC. Give us something of their internal world, their day-to-day, make them a fully realised human. Then you can throw them into action.
It's not that you can't start in medias res, pique the readers' curiosity first with a tense scene, then go back and explain how we got there. But then, the explanation, or at least some sort of introduction to the characters, has got to come sooner than 20 pages in.
Yes. Write it anyway.
Because here you are at the very beginning of a novel second guessing yourself. At this stage, the most important thing is that you are sitting down writing. So write.
When you are further into the story, go back and reassess. Maybe the action works, maybe it needs to be cut down, or even cut entirely. Maybe it needs to be moved, or broken up in to pieces. Or fleshed out so it's not so intense and single-minded.
And maybe you'll find yourself with half a book length of nothing but action scenes that aren't really a novel. Then you can start on something that incorporates part of that action. Or not. Either way, you will be much better at writing action than you were before you started.
The other thing is to find people to read what you write. Not in the very beginning, but after you're in to it some. A writer's group is the best way, because then you all commit to read each other's work on a regular basis. Because maybe your action is a full-fledged story. Or maybe it's too much. Only people who read it will know.