While there is no way to avoid them, there is a way to give lvl 40 girls books. Although it doesn't count for the contest, so it's just useless... They really should just enable it and let it count despite not adding xp, it shouldn't be too hard. Just need to not disable it on level 40 and add the xp value to the contests point counter even if it doesn't let you actually give xp to the girl (so basically just counting it as "book with xp value of X was used" instead of "girl Y gained X xp"). :P