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Heh... to level up magic for a Barbarian, you need to have a Castle that offers that magic... and if you have a Castle, it's better to use a Mage with that magic, as they have more mana and skills (although light mages can reduce Battle Dodge). (In general, it's already low for me... and it's different for everyone :\... I don't know why... even though they're all the same race, I leveled up the Tactics skill for the leader, and it's at 5, while the mobs have less...)
P.S. Relying on books... hmm... isn't a very good option either), so it's better to focus on combat + tactics... or maybe even another hero).