Aside from a book about laws, histories, wonderful and amazing characters, and poetry, the Bible also talks a great deal about hope. Hope is necessary when things are not going our way, and that was exactly our destiny because of sin.
Sin imprisoned mankind, and as a result all of mankind should have been bound to hell, but Jesus Christ paid for those sins, and now offers mankind a chance to go to heaven. The famous John 3:16 says anyone who would believe in Jesus would not perish but have everlasting life.
This everlasting life is given permanently to those who place their faith in Jesus. 1 John 5:13 says that the Bible was written to inform those who have faith in Jesus that they have eternal life. That means salvation can be assured, because God says so.