Use Books of Death only once?

[Lucans]

I entered Death Land, bumped into strong enemy troop, got thrown out. Levelled up a bit. Went back using the second Book of Death, did some quests but got thrown out again.

Now I can't activate the Books of Death anymore. I've been back to every castle, in every land, talked to every NPC again, did all the other quests available to me. Still can't click the Books of Death.

Are they only supposed to be used once?
How do you return after finishing quests?