I personally would not recommend it. The intent behind uploading excerpts is to generate interest and inspire people to pre-order so they can get the rest of it. If you give them the whole thing for free, they lose the incentive to pay for it. That being said, there really is no one right way to run a campaign, and it’s entirely possible that your idea might work. I’ve just not seen it happen.
I was just about to ask about this. My idea was to take a 25 chapter book, release the first couple of chapters, and then release a following chapter after 30 preorders each.
Andy Weir posted his story online as a serial - he wasn’t really intending to publish it and sort of stumbled backwards into having an enormously successful book. Readers of his blog (I think it was on a blog) asked him to make it available as an ebook for easier reading, and he put it up on Amazon for 99c because he couldn’t put it for free. :D
What he DID have, because he wrote it as a serial online for free, was a big online following and an amazing book. Hugh Howey is another highly successful online author who wrote serially (I think) and then self-published. (If you haven’t read Wool, stop everything and do it immediately!)
All this is to say that you should probably have enough attached to your campaign page to give your potential readers a taste of your story, writing style, and hopefully a hook into the main plot. Don’t give away all the milk for free? Most of your work after you ’go live’ and start accepting preorders should not go into creating more content for your book, but getting into all the social media outlets you can get your fingers into.
Book one in a character-driven middle reader series about an Alaska Native teenager living in small-town Alaska. While helping his dad at the Moose Like Espresso Cafe, Rigs Seward gets a firsthand look at the locals, and all of their local drama.
That being said, there really is no one right way to run a campaign, and it’s entirely possible that your idea might work. I’ve just not seen it happen.