A memorization tip based on grammar: كِتَاب meaning "book" derives from a verbal noun كِتَابَة "writing" from the verbal root كَتَبَ meaning "to write". The active participle (performer of the action) is derived with long a and short i: كَاتِب meaning "writer". Other examples for this pattern are وَلَدَ "to give birth" -- active participle وَالِد "parent, father", وَالِدَة "mother" -- verbal noun وِلَادَة "birth, bring to life" -- وَلَد "boy, child".