some progress

app/Models/Book.php

@@ -16,6 +16,14 @@ class Book extends Model
         'category_id',
     ];
 
+    /**
+     * Use slug for route model binding and URL generation.
+     */
+    public function getRouteKeyName(): string
+    {
+        return 'slug';
+    }
+
     /**
      * Get the category that owns the book.
      */
@@ -31,4 +39,36 @@ class Book extends Model
     {
         return $this->hasOne(Summary::class);
     }
+
+    /**
+     * The authors that belong to the book.
+     */
+    public function authors()
+    {
+        return $this->belongsToMany(Author::class, 'author_book')->withTimestamps();
+    }
+
+    /**
+     * Users who saved this book to their readlist.
+     */
+    public function savedByUsers()
+    {
+        return $this->belongsToMany(User::class, 'readlist_items')->withTimestamps();
+    }
+
+    /**
+     * Reports submitted for this book's summary.
+     */
+    public function reports()
+    {
+        return $this->hasMany(SummaryReport::class);
+    }
+
+    /**
+     * Reviews left by users for this book's summary.
+     */
+    public function reviews()
+    {
+        return $this->hasMany(SummaryReview::class);
+    }
 }