body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  text-align: center;
}

header {
  background-color: #f4f4f4;
  padding: 20px;
}

main {
  padding: 20px;
}

#book-selection button {
  margin: 10px;
  padding: 10px 20px;
  font-size: 16px;
}

#content-display {
  margin-top: 20px;
}