3 months after I started, I launched the MVP publicly which had bare minimum features and only 15 chapters! (Now there's 36).
Because it was an MVP, I made the price cheaper (launch discount) and I showed which chapters I plan on publishing and even the expected date when the next chapter will be launched (to show the users that this is actually in heavy development).
The first 4 chapters were free and they were asked to upgrade with a one time payment once they reach chapter 5.