diff --git a/src/hooked_containers/container.py b/src/hooked_containers/container.py
index e80ea15..e76483f 100644
--- a/src/hooked_containers/container.py
+++ b/src/hooked_containers/container.py
@@ -15,6 +15,7 @@ class HookFunction(Protocol):
 
 
 class HookedContainer(ABC, Sized, Iterable[T], Container[T]):
+    _data: MutableNesting[T]
     _path: MutableSequence[int]
     _root: MutableMapping[T] | MutableSequence[T] | None = None
     hook: HookFunction
@@ -22,15 +23,21 @@ class HookedContainer(ABC, Sized, Iterable[T], Container[T]):
     def __repr__(self):
         return f"{self.__class__.__name__}({self._data!r})"
 
+    def __len__(self):
+        return len(self._data)
+
+    def __iter__(self):
+        return iter(self._data)
+
+    def __contains__(self, x):
+        return x in self._data
+
     # Sequence Methods
     # __contains__, __iter__, __reversed__, index, and count
 
     @abstractmethod
     def __getitem__(self, key): ...
 
-    def __len__(self):
-        return len(self._data)
-
     # MutableSequence Methods
     # append, reverse, extend, pop, remove, and __iadd__
 
@@ -44,8 +51,8 @@ class HookedContainer(ABC, Sized, Iterable[T], Container[T]):
         if self.hook:
             self.hook(e.RemoveItemEvent(self.new_path(s), item))
 
-    @abstractmethod
-    def insert(self, index, value): ...
+    # @abstractmethod
+    # def insert(self, index, value): ...
 
     # Custom Methods
 
diff --git a/src/hooked_containers/mapping.py b/src/hooked_containers/mapping.py
index e19ce6b..f993329 100644
--- a/src/hooked_containers/mapping.py
+++ b/src/hooked_containers/mapping.py
@@ -16,52 +16,41 @@ class HookedMapping(HookedContainer[T], MutableMapping[T, MutableNesting[T]]):
         hook: HookFunction | None = None,
         path: MutableSequence[int] | None = None,
     ):
-        self.hook = hook
         match existing:
             case HookedMapping(_data=seq):
                 self._data = seq
             case MutableMapping() as seq:
                 self._data = seq
-            case _ as it:
-                self._data = dict(it)
+            case _:
+                raise TypeError(f"Expected a mapping, got {type(existing)}")
+                # self._data = dict(it)
         self._data = existing
+        self.hook = hook
         self._path = list(path) if path is not None else []
 
-    # MutableMapping Methods
-
-    def __iter__(self):
-        return iter(self._data)
-
-    def insert(self, key: T, value: MutableNesting[T]) -> None:
-        self._data[key] = value
-        if self.hook:
-            self.hook(e.AddItemEvent(self.new_path(key), value))
-
-    # HookedContainer methods
-
     def __getitem__(self, key: T) -> MutableNesting[T]:
         if key not in self._data:
-            self.insert(key, {})
-            return HookedMapping(self._data[key], hook=self.hook, path=self.new_path(key))
+            return self.__setitem__(key, {})
         value = self._data[key]
         match value:
-            case HookedMapping(_data=seq):
-                return type(self)(seq, hook=self.hook, path=self.new_path(key))
             case MutableMapping() as mapping:
                 return HookedMapping(mapping, hook=self.hook, path=self.new_path(key))
             case _ as item:
                 return item
 
-    def __setitem__(self, key: T, value: MutableNesting[T]) -> None:
-        if key not in self._data:
-            self.insert(key, value)
-        else:
-            self._data[key] = value
-            if self.hook:
-                self.hook(e.SetItemEvent(self.new_path(key), value))
+    def __setitem__(self, key: T, value: MutableNesting[T]) -> MutableNesting[T] | None:
+        new_path = self.new_path(key)
+        event = e.SetItemEvent(new_path, value) if key in self._data else e.AddItemEvent(new_path, value)
+        match value:
+            case HookedMapping(_data=value):
+                self._data[key] = value
+            case _:
+                self._data[key] = value
+        if self.hook:
+            self.hook(event)
+        return value
 
     def __delitem__(self, key: T) -> None:
-        item = self._data[key]
-        del self._data[key]
+        item = self._data.pop(key)
         if self.hook:
             self.hook(e.RemoveItemEvent(self.new_path(key), item))