I do that with the Wheel of Time series. Apparently the names of a lot of these nouns have different pronunciations than what I originally thought. For instance:
Aes Sedai - Supposed to be pronounced as "EYES sed-EYE", but I've always pronounced it as "Ays SEH-die"
Egwene - Supposed to be pronounced as "e-GWAIN", but I've always pronounced it as "EGG-win"
It wasn't really an issue until I sat in on the WoT panel with Branden Sanderson at this past Phoenix Comicon and he pronounced everything strangely.