There is a foul legend that God in the Old Testament is something less than Love. But God is Love, and God does not change, therefore if we do not see that God in the Old Testament is Love, then our understanding needs to change. The God of the Old Testament is exactly the same as of the New--who sees Jesus sees the Father (Jn 14:9).
Slide from Talk 4, illustrating how Old Testament books relate to Jesus Christ
During the recent series of talks at St Mary's Shrine on 'Discovering Jesus Christ in the Old Testament' (full slide show available here as pdf) there was an enthusiastic response to a list of chapters from the Old Testament showing the tenderness of God's Love and His hatred of injustice. Once we see that God is Love throughout the Ages, then we have a basis for approaching those passages in the Old Testament which are more difficult to understand.
Below is part of this list. Please do add comments below for other passages which you think deserve to be added:
Psalm 93 (Begins: “The LORD is the God to Whom revenge belongs”. Some number it as Psalm 94)
Psalm 144 (Begins: “I will extol Thee, my God and King”. Some number it Psalm 145)