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.
"And Abraham was an hundred years old, when his son Isaac was born unto him. And Sarah said, God hath made me to laugh, so that all that hear will laugh with me. And she said, Who would have said unto Abraham, that Sarah should have given children suck? for I have born him a son in his old age."
Abraham went on to live until he was 175 years old