Absorb Spell (Su): Beginning at 7th level, if a spellthief makes a successful save against a spell that targets him, he can attempt to absorb the spell energy for later use. This ability affects only spells that have the spellthief as a target, not effect or area spells (at least until 13th level, see below). A spellthief can't absorb a spell of a higher level than he could steal with his steal spell ability (see above).
To absorb a spell that targets him, a spellthief must succeed on a level check (1d20 + spellthief level) against a DC of 10 + the spell's caster level. Failure indicates [...] the spell has its normal effect. Success means that the spellthief suffers no effect from the spell and can cast the spell later (or use its energy to cast one of his own spells known) as if he had stolen the spell with his steal spell ability. His normal limit of total spell levels stolen still applies.
If a spell targets the spellthief but only allows a saving throw for a partial effect, if he makes a successful save and then succeeds on his level check, he absorbs the spell without suffering even that partial effect (such as half damage from a fireball). If a spell targets the spellthief but normally does not allow a saving throw, the spellthief is allowed to attempt as special save against what the spell's DC would be if it had one (type determined by DM as appropriate, for example, a Reflex save against scorching ray). If he succeeds at the special saving throw he can attempt his level check to absorb the spell without harm, but if he fails either the saving throw or the level check, he suffers the full effect of the spell as normal.
At 13th level or higher, a spellthief can attempt to absorb even effect or area spells that would affect him. At 19th level or higher, a spellthief can choose to use the stolen spell energy as an immediate action, either to recast the original spell or to cast one of his own spells.
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