Found them inside few files at out\com\bn\nook\reader\commonui (I just opened ALL the files of this folder in Notepad++ and did search for font names across all of them).
I have replaced some the stock fonts just by renaming and replacing them. Now I would like to see their real names. There are so many mentions of the fonts, even inside such strings:
.field public static final FONT_FAMILY_GILLSANS:Ljava/lang/String; = "Gill Sans"