First there were the Jews, with their holy book; then there were the Christians, with their holy book; and then there were the Muslims, with their holy book. Together they formed the three major monotheistic religions, with lots in common and lots not.
Christianity, a cult of Judaism that eventually had enough members to rise to the status of sect, became a separate religion when they added their own holy book, the New Testament. For some Christians, this superseded the Old Testament (which Jews call the Hebrew Bible), though Christians also consider the Old Testament holy. Jesus said he did not come to change one jot or tittle from the old law. Subsequent bibles actually contain anywhere from 24 to 66 books, depending on sect. Muslims much later added their own holy book (the Quran), but also consider the Jewish and Christian bibles holy.
Each religion added at least one prophet. Jews had Noah, Abraham, and Moses, and then Christians added Jesus (who is also somehow the God of the Old Testament, as well as being his own son). Muslims kept all these prophets and added Muhammad.
Here's what else these three religions have in common. If you can find an interpretation in one holy book to justify an atrocity, then you can most likely find a comparable interpretation and justification in the other holy books. These include genocide, holy wars, slavery, misogyny, and death for crimes like blasphemy, homosexuality, and worshipping the wrong god or even the right god in the wrong way.
I'm not interested in trying to decide the best and worst "holy" books because all contain both ridiculous and reasonable passages. Adherents can quote portions to justify loving their neighbor or killing their infidel neighbor. I'm more interested in behavior than belief. Some religious fundamentalists will find relatively benign interpretations of terrible passages, while some liberal religionists will either ignore uncomfortable passages or treat them as metaphors.
As an atheist, it's easy for me to read portions of ancient books written by fallible humans and follow only what makes sense to me. I believe (along with most biblical scholars) that Noah, Abraham, and Moses never existed, that Jesus probably existed, and that Muhammad definitely existed. I also believe that nobody died and returned, and nobody traveled up or down to a nonexistent heaven or hell.
Today, we see more Muslims invoke their holy texts to justify violence than do adherents of any other religion. Often these atrocities are inspired or justified by passages in the Quran that are similar to those from Judaism or Christianity. Recently, Islamic militants ransacked Mosul's central museum, destroying priceless artifacts because they represented idols. That reminded me of the biblical story of Abraham smashing his father's idols instead of worshipping the one "true" God. And when the Islamic State indiscriminately kills innocent people, I think of the quote from a Christian abbot in the midst of a Crusade: "Kill them all, let God sort them out."
I prefer the Crusades to the Islamic State only because the Crusades ended in the thirteenth century. Most Christians have learned to be more tolerant and secular, and I hope that Muslims will also have their twenty-first century Enlightenment. Of course, I'm not so concerned with people who have ludicrous religious beliefs as long as their beliefs don't interfere with those who don't share such beliefs.
Which brings me to Michele Bachmann, the 2012 candidate for the Republican presidential nomination who recently predicted that the rapture will be coming soon because of President Barack Obama's policies on Iran's nuclear program and marriage equality. Bachmann seemed upset by such pursuits, though I would think she'd now be a strong supporter of Obama since he will hasten the return of Jesus. Then again, Christians in previous generations (and some today) hate the Jews for killing Christ even though Jesus supposedly came on purpose to be killed so that his blood could "save" Christians. Go figure.
I'm happy to live in a country where Michele Bachmann has the free speech right to say whatever she wants about Obama or anyone else, and I have the free speech right to call Bachmann an idiot. And I'm very happy to live in a country where people can choose to be Jews, Christians, Muslims, atheists, and any other religion or non-religion, without being prosecuted as a heretic.