It needs to be made clear that Spellcraft won't let you learn spell you can't cast.
The wording is poor enough that you can argue its possible to learn spells from other classes, spells of a higher level than you can cast, and spells not normally on your list but on someone's Sorcerer or Wizard list (Dragons and Nagas both have these).
Its a single line of text, but it would save a lot of arguments (and with the Bonded Object power, some abuse).