What he said. It's also revealed in Fe7 that anima is the easiest form of magic to control, as explained in Canas's supports with Nino. It's also why Hugh, Canas's son in Fe6, prefers anima to become a mage, instead of a shaman, as explained in their B support, as Hugh cries, when Canas shows him flux. :P wimp.
Also, for anima magic, the connection to the spellbook is weaker than others, as it is revealed that Nino can't read, and so, she just copied the sounds Sonia made, and learned to cast fire just by imitating Sonia's words like a parrot.
And if you think that's right... Soren should have been able to memorize all of his spells in 3 years then have to look at a dumb book. -_-