Today is the feast of St. Louis de Montfort. Demontfort (31 January 1673 – 28 April 1716) was a French priest whose work, True Devotion to Mary, is still generally thought to be the best single volume on devotion to the Blessed Mother.
Saint John Paul the Great once recalled how, as a young seminarian, he “read and reread [True Devotion to Mary] many times and with great spiritual profit. … Then I understood that I could not exclude the Lord’s Mother from my life without neglecting the will of God-Trinity.” 
Here are 5 quotes from Demontfort from that book.
“With the whole Church I acknowledge that Mary, being a mere creature fashioned by the hands of God is, compared to his infinite majesty, less than an atom, or rather is simply nothing, since he alone can say, ‘I am he who is’. (14)
“Satan fears her not only more than angels and men but in a certain sense more than God himself. This does not mean that the anger, hatred and power of God are not infinitely greater than the Blessed Virgin’s, since her attributes are limited. It simply means that Satan, being so proud, suffers infinitely more in being vanquished and punished by a lowly and humble servant of God, for her humility humiliates him more than the power of God.”(52)
“When the Holy Spirit, her spouse, finds Mary in a soul, he hastens there and enters fully into it. He gives himself generously to that soul according to the place it has given to his spouse.” (36)
“Mary is the Queen of heaven and earth by grace as Jesus is king by nature and by conquest. But as the kingdom of Jesus Christ exists primarily in the heart or interior of man, according to the words of the Gospel, “The kingdom of God is within you”, so the kingdom of the Blessed Virgin is principally in the interior of man, that is, in his soul. It is principally in souls that she is glorified with her Son more than in any visible creature. So we may call her, as the saints do, Queen of our hearts.” (38)
“She is so full of love that no one who asks for her intercession is rejected, no matter how sinful he may be. The saints say that it has never been known since the world began that anyone had recourse to our Blessed Lady, with trust and perseverance, and was rejected.”(85)