RemixIconEx.Document.book_open

You're seeing just the function book_open, go back to RemixIconEx.Document module for more information.
Link to this function

book_open(icon_css_class \\ "icon")

iex> Elixir.RemixIconEx.Document.book_open()
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" class="icon">
  <path d="M13 21v2h-2v-2H3a1 1 0 0 1-1-1V4a1 1 0 0 1 1-1h6a3.99 3.99 0 0 1 3 1.354A3.99 3.99 0 0 1 15 3h6a1 1 0 0 1 1 1v16a1 1 0 0 1-1 1h-8zm7-2V5h-5a2 2 0 0 0-2 2v12h7zm-9 0V7a2 2 0 0 0-2-2H4v14h7z" />
</svg>

example usage

svg.icon {
  width: 96;
  height: 96;
}