Why don't you recite Leviticus?
Frankly if you need to atone for sins by making some sacrifice in reading scripture, I would think that having to recite a few chapters of Leviticus would go a long way further towards making a person think twice about repeating a sin than having to recite a few hundred Hail Marys.
Tell me, as a penance after confession, have you ever been asked to recite a chapter or two from Leviticus?
If so, have you ever repeated THAT sin?
We study and incorporate the lessons of Levciticus into our worship, but the Old Testament only a prepratory test for the coming of Jesus and was fulfilled by His death and resurrection.
Catholic worship and prayer is concentrated on a new 10 commandments as enumerated by Christ Himself. These are the two greatest commandments He gave us and the eight Beatitudes.
Love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength.
Jesus added a second command, that we must love our neighbor as ourself.
"Blessed are the poor in spirit, for theirs is the kingdom of heaven.
Blessed are they who mourn, for they shall be comforted.
Blessed are the meek, for they shall inherit the earth.
Blessed are they who hunger and thirst for righteousness, for they shall be satisfied.
Blessed are the merciful, for they shall obtain mercy.
Blessed are the pure of heart, for they shall see God.
Blessed are the peacemakers, for they shall be called children of God.
Blessed are they who are persecuted for the sake of righteousness, for theirs is the kingdom of heaven."