Tuck Everlasting by Natalie Babbit

Tuck Everlasting is about a family who's last name was Tuck. They found a spring of water that made them live forever. They couldn't be killed by anything. One day, a girl named Winny Foster found the spring. But a boy from the Tuck family stopped her from drinking it, and took her to his house. The Tuck family explained to her about the spring, and told her that they regretted it. They told her that she should never drink it. Winny became very good friends with the Tucks, and helped them in a time of need.