Crazed - We are all busy and pressed for time and reading and commenting on chapters takes a lot of time. So, some suggestions:
1) Post short excerpt of a chapter, no more than 5-6 pages and make sure there is lots of "white space" and pictures to break up the text and encourage people to keep reading.
2) Who else is writing a similar book or stories on HP? Are you willing to spend serious time reading and commenting on their work? Contact them and see if they are willing to trade with you.
3) Print a chapter out -- make a hard copy. Do not look at it at all for 4-5 days. Now read it slowly out loud listening for mistakes and areas that feel rough or need to be tinkered with. Make corrections in pencil as you go. We read too fast and have a harder time correcting out own work when we read silently.
4) There is a;ways the old-fashioned way, but you will have to leave your house and meet with real people. Find a local writer's club (or start one - usually meet once or twice a month) where everyone exchanges chapters at each meeting and edits each other's work before the next meeting. Develop a tough hide - be prepared for criticism - that s how we get better. Good Luck. :)