RemixIconEx.Document.book_3

You're seeing just the function book_3, go back to RemixIconEx.Document module for more information.
Link to this function

book_3(icon_css_class \\ "icon")

iex> Elixir.RemixIconEx.Document.book_3()
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" class="icon">
  <path d="M21 4H7a2 2 0 1 0 0 4h14v13a1 1 0 0 1-1 1H7a4 4 0 0 1-4-4V6a4 4 0 0 1 4-4h13a1 1 0 0 1 1 1v1zM5 18a2 2 0 0 0 2 2h12V10H7a3.982 3.982 0 0 1-2-.535V18zM20 7H7a1 1 0 1 1 0-2h13v2z" />
</svg>

example usage

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