I’ve never read the Old Testament, let alone the whole Bible, in its entirety. Even so, it’s impossible for me to read it and not want to literally slap God in the face for murdering all of those people and what not.
It's a natural sentiment to have at times. That said it's a little... I guess cursory would be the best word. Much of the anger or confusion at God's actions are based on a failure to maintain a a proper creator/creature distinction or an overly positive view of humanity. Once those points are nailed down, the questions change.
Rabbis have been discussing these aspects of the OT for thousands of years and their perspectives are generally a lot fresher than the stale "muh Old Testament harsh and punishing God and muh New Testament gentle and forgiving God" takes in this thread.
On a related note, this has been one of the weakest points in Evangelical catechesis. When the tensions between the "two Gods" of this approach are inevitably pointed out, there's a tendency towards either umbelief like the poster above you, or Andy Stanley style quasi-Marcionism.
Evangelical churches would do well to make sure their people learn about the safrificial system pointing us to Christ, the faith of the patriarchs etc. Basically, a good strong dose of Hebrews would do wonders here.