The word genesis means 'beginning' - an appropriate title for the book of the same name. Not only is it the beginning of the Bible, being the first book, it also tells of the beginning of the world and how it was created by God. The Book of Genesis also describes how sin came into the world and how God exercises His judgement, but also His mercy, on mankind.
Genesis 22:16-18
"and said, By myself have I sworn, saith the Lord, for because thou hast done this thing, and hast not withheld thy son, thine only son: that in blessing I will bless thee, and in multiplying I will multiply thy seed as the stars of the heaven, and as the sand which is upon the sea shore; and thy seed shall possess the gate of his enemies; and in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice."
Abraham's 'seed' includes the entire Jewish people and Jesus Christ