I've noticed things do sometimes get done wrong. Some of the GoF "goofs" are totally stupid, like talking about how Mad Eye's eye patch keeps switching from his left to his right eye during his first office meeting with Harry. Well, duh! Sometimes he's looking in a mirror, sometimes not!
I've also seen some actors in movies, and then can't find them in the credits on IMDb.
Still, it's a really good source, I think. Most of the time it's pretty accurate. You'd think Robert's agent would get that fixed!
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I've read the trilogy only twice. There have been a few books I've read more than once, but not too many. One was "A Woman of Substance," which, I suppose, was actually a fairly predictable romance novel. It inspired me though, because the heroine wanted her own business and really worked hard for it! I think if I read the Trilogy again I'd pay more attention to the poems and songs, which I saadly admit I kinda skipped over sometimes.