A wizard can add a spell to her spellbook by copying another's spellbook.
1. Decipher the magical writing: Spellcraft DC 20 + spell level; retry in one day
2. Study the spell for one hour: Spellcraft DC 15 + spell level; +2 bonus of specialized in the same school; retry in one week
3. Copying the spell takes 1 hour per spell level (30 minutes for cantrips), and a cost in materials, as listed below.
Lyrie's Spellbook
acid splash, burning hands, comprehend languages, detect magic, detect secret doors, floating disc, grease, identify, invisibility, locate object, mage armor, minor image, mirror image, obscuring mist, prestidigitation, ray of enfeeblement, ray of frost, see invisibility, sleep. shatter, spider climb
Caizarlu's Spellbook
acid arrow, bleed, blindness/deafness, cause fear, chill touch, command undead, detect magic, displacement, false life, gentle repose, ghoul touch, halt undead, identify, light, mage armor, mage hand, magic missile, mirror image, obscuring mist, prestidigitation, ray of enfeeblement, stinking cloud, vampiric touch
Wizard's Spellbook
blink, cat's grace, chill touch, enlarge person, fox's cunning, grease, haste, lightning bolt, mage armor, magic missile, scorching ray, shocking grasp, shrink item, spider climb, web