index.html.erb

<p id="notice"><%= notice %></p>

<h1>Books</h1>

<table>
  <thead>
    <tr>
      <th>Isbn</th>
      <th>Title</th>
      <th>Year published</th>
      <th>Author</th>
      <th>Categories</th>
      <th>Recommendations</th>
      <th colspan="3"></th>
    </tr>
  </thead>

  <tbody>
    <% @books.each do |book| %>
      <tr>
        <td><%= book.isbn %></td>
        <td><%= book.title %></td>
        <td><%= book.year_published %></td>
        <td><%= book.author.try(:name) %></td>
        <td>
          <ul>
          <% book.categories.each do |category| %>
            <li><%= link_to category.name, category %></li>
          <% end %>
          </ul>
        </td>
        <td><%= (@recommendations[book.isbn] || []).map(&:title).to_sentence %></td>
        <td><%= link_to 'Show', book %></td>
        <td><%= link_to 'Edit', edit_book_path(book) %></td>
        <td><%= link_to 'Destroy', book, method: :delete, data: { confirm: 'Are you sure?' } %></td>
      </tr>
    <% end %>
  </tbody>
</table>

<br>

<%= link_to 'New Book', new_book_path %>