Association I - Bookmarks project - last step

https://www.codecademy.com/courses/learn-rails/projects/learn-rails_bookmarks

When I try to display my finished project on browser, I get:

"# NameError in Books#show

Showing /home/ccuser/workspace/learn-rails_bookmarks-2/bookmarks/app/views/books/show.html.erb where line #2 raised:

undefined local variable or method `book' for #<#<Class:0x000000041aea60>:0x000000041adb88>
Did you mean?  @book

Extracted source (around line #2 ):

1 2 3 4 5

<%= book.title %>

by <%= book.author %>

( <%= book.publisher %> )

<%= book.description %>

"

But the file that this error seems to say is wrong seems fine to me:

<%= book.title %>

by <%= book.author %>

( <%= book.publisher %> )

<%= book.description %>

What am I doing wrong?