A Catholic supplement to the Bible. Despite the fact that many Catholics (and Christians for that matter) rarely read the Bible, much less the catechism, BOTH books are incredibly important to
understanding the Catholic faith.
It is analogous to reading the Tanakh, the Mishna, and the Talmud - which is what studious, ambitious, pious Jews do to develop their faith and be better Jews.
Similarly, reading and
understanding the Bible AND the Catechism of the
Catholic Church will strengthen the faith of Catholics.