Deadline by Chris Crutcher

Crutcher is known as an author of books for young people, but I think this one would appeal to high school students as well. Ben, the protagonist, is a senior in high school who is diagnosed with an unnamed terminal illness. Because he is 18, he demands that his illness be kept secret from everyone, even his family. Ben decides there are some things he wants to do before he dies, and he sets about accomplishing them. I really liked the relationship between Ben and his brother--finally, two siblings who actually like each other! As you read, you cannot help but think about the things you choose to do in your own life. It also makes you look a little bit more closely at the people around you and what is going on in their life. Warning: the ending is very sad.