Answer:
The book of Genesis contains many truths without which the rest of the Bible would be incomprehensible.
The following is a list of the key truths mentioned in Genesis:
God as Creator
Origin of the human race
Origin of sin
First promise of a remedy for sin
Origin of marriage and family
God's judgment on sin in the flood, a type of the judgment to come
Origin of diverse languages
Origin of nations
Origin of the Jewish nation
Some people would suggest that Genesis should not be taken literally. Jesus not only took it as literal history but quoted from it as authoritative such as in giving God's original will in regard to marriage.