It has been 21 years since the horrific attacks on the World Trade Center. Thousands of lives were lost, and our nation was forever changed. Despite the years gone by, we are still healing. We will never forget the horrors of that day, and we will always remember the heroism of those who went into the rubble and fire to save others. Check out these three books that share stories from that terror-filled day, and memorialize the thousands of lives lost.