Originally Posted by abatsukh
I tried both ways and still alot of question marks appear on the book. is it because the book is in spanish?
Spanish is included in cp1252, so if you have tried cp1252 and utf-8 I'm not sure what else to suggest. Other possibilities include macintosh for Mac OS Roman and IBM's cp850. I don't know if Calibre will recognize these code sets though. See Western Latin character sets (computing)
. It probably is worth trying macintosh at least.