Emberjs not converting JSON to model array

From my Emberjs I am making a custom request to an explore route on my Rails server:

GET http://localhost:3000/explore

I see my JSON response in my Google Chrome network inspector, however, my page isn't rendering anything.

To make the custom request, I have a book adapter:

Book Adapter

import ApplicationAdapter from './application';
import Ember from 'ember';

export default ApplicationAdapter.extend({
  apiManager: Ember.inject.service(),

  findPublishedBooks: function(store, type) {
    let jwt = this.get('apiManager').get('jwt');

    return Ember.RSVP.resolve(
      Ember.$.ajax({
        type: "GET",
        url: this.get('apiManager').requestURL('explore'),
        dataType: 'json',
        headers: {"Authorization": "Bearer " + jwt}
      })
    );
  }
});

Explore Route

model() {
  const adapter = this.get('store').adapterFor('book');
  return adapter.findPublishedBooks();
}

On my Rails side, I have this for my Explore action:

Rails Explore Action

def explore
  books = Book.where(published: true)

  if books.count > 0
    render json: books
  else
    return nil
  end
end

I know I must be doing something wrong, probably on my Ember side.