Update Controller not work in laravel

** update Controller in laravel 5.1.11 **

///////////////////////////////////////////////////////////

namespace App\Http\Controllers;

use App\Book;

use App\Http\Requests;

use App\Http\Controllers\Controller;

use Illuminate\Http\Request;

class BookController extends Controller {

public function edit($id) {

$book=Book::find($id);

return view('books.edit',compact('book')); }

public function update($id){

$bookUpdate=Request::all();

$book=Book::find($id);

$book->update($bookUpdate);

return redirect('books');

}

}

///////////////////////////////////////////////////////

**My url

http://localhost:8000/books/14

///////////////////////////////////////////////////////

** My browser show this problem

Whoops, looks like something went wrong.

1/1 ErrorException in BookController.php line 56:

Non-static method Illuminate\Http\Request::all() should not be called statically, assuming $this from incompatible context

via Chebli Mohamed