How to optimize and shorten the code (hash parsing in ruby)?

Question

ruby

Actually here is a link to the code REPL.it
There is a hash:

[
  {
    part: 'one',
    books: {
      rowling: {book: 'Harry Potter', year: 1997},
      martin: {book: 'Game of Thrones', year: 2011},
    }
  },
  {
    part: 'two',
    books: {
      rowling: {book: 'Harry Potter', year: 1997},
      martin: {book: 'Game of Thrones', year: 2011},
      tolkin: {book: 'The Lord of the Ring', year: 2001}
    }
  },
]

I need to parse in such a way that I get the following result:

# Expect Result Output после uniq и сортировки по author
{:author=>:martin, :book=>"Game of Thrones"}
{:author=>:rowling, :book=>"Harry Potter"}
{:author=>:tolkin, :book=>"The Lord of the Ring"}

Any ideas how to implement this in a shorter and more efficient way?
The function that I wrote, I use as many as 3 iterations over the array ( map , each , each ) and at the end sort_by ...

Answer 1

arr
  .reduce({}){|acc, n| acc.update(n[:books])}
  .collect{|k, v| { author: k, book: v[:book] }}
  .sort_by{|n| n[:author]}