Adults shouldn't find the books to be as exciting as kids. IMHO they are written for the 9-13 age range. I applaud any series that could have the kids this excited.
As far as the religous angle. I have a very good friend who is a youth minister and doesn't allow his kids to trick or treat, avoids fairy tails, etc. I find it to be amusing. My kids were mature enough at age 8 to figure out and understand the difference between stories like Harry Potter and our religous beliefs. I assume that most 8 year olds can as well. Teaching kids to think and differentiate will do more to instill a sense of being and religion than hiding Harry Potter from them. Can you imagine this conversation "Daddy, do you really believe Nancy is going to hell from reading Harry Potter? Then all my friends are wrong."