.book-summary ul.summary li.accordion-header {
  cursor: pointer;
  user-select: none;
  position: relative;
  padding-right: 1.5em;
}

.book-summary ul.summary li.accordion-header::after {
  content: '\25BE';
  position: absolute;
  right: 0.75em;
  top: 50%;
  transform: translateY(-50%);
  transition: transform 0.25s ease;
  font-size: 0.75em;
}

.book-summary ul.summary li.accordion-header[aria-expanded="false"]::after {
  transform: translateY(-50%) rotate(-90deg);
}

.book-summary ul.summary ul.accordion-section {
  list-style: none;
  padding: 0;
  margin: 0;
  overflow: hidden;
  transition: max-height 0.25s ease;
}