"Westing game"
The name of a book should be capitalized and underlined.
"In Sam Westing's will, he states that the But the catch is that one person out of sixteen people is actually the true heir. "
He states what? What is "that"? "But" doesn't need to be capitalized.
"It is about a man who is murdered and leaves 200,000,000(200 million) dollars to a person. The man's name is Sam Westing. In Sam Westing's will, he states that the But the catch is that one person out of sixteen people is actually the true heir."
Very wordy and confusing. "The man's name is Sam Westing" should be combined with another sentence.
"The sixteen people are paired up into groups of two and each group is given a clue to the mystery. "
What mystery?
Frankly, you need to provide a bit more detail about the book. Make it concise and interesting. Also, your title says "one page summary"; this is nowhere near one page.
Good luck!
Henry Lin