diff --git a/src/pystac/item.py b/src/pystac/item.py
index 107556048..7107de576 100644
--- a/src/pystac/item.py
+++ b/src/pystac/item.py
@@ -89,6 +89,13 @@ def __init__(
 
         self._collection: Collection | str | None = collection
 
+    @classmethod
+    def try_from(cls, data: dict[str, Any] | Item) -> Item:
+        if isinstance(data, Item):
+            return data
+        else:
+            return cls(**data)
+
     @override
     @classmethod
     def from_dict(
diff --git a/src/pystac/item_collection.py b/src/pystac/item_collection.py
index f47e5c10e..1ec2e4e8d 100644
--- a/src/pystac/item_collection.py
+++ b/src/pystac/item_collection.py
@@ -1,10 +1,15 @@
 from __future__ import annotations
 
 import copy
+import warnings
 from collections.abc import Iterator
 from pathlib import Path
 from typing import Any, Literal, TypedDict, override
 
+from typing_extensions import deprecated
+
+from .container import Container
+from .errors import STACTypeError
 from .item import Item
 from .reader import DEFAULT_READER, Reader
 from .utils import make_absolute_href
@@ -16,9 +21,24 @@ class T_ItemCollection(TypedDict):
 
 
 class ItemCollection:
-    def __init__(self, items: list[Item], **kwargs: Any):
-        self.items: list[Item] = items
+    def __init__(self, items: list[Item], root: Container | None = None, **kwargs: Any):
+        self.items: list[Item] = [Item.try_from(item) for item in items]
+
+        if "root" in kwargs:
+            raise KeyError(
+                "root is not a valid key word argument to ``ItemCollection()``. "
+                "If root is required try instantiating the items directly and "
+                "providing root."
+            )
+
+        extra_fields = kwargs.pop("extra_fields", {})
         self.extra_fields: dict[str, Any] = kwargs
+        if extra_fields:
+            warnings.warn(
+                "Pass extra_fields entries as kwargs, "
+                "instead of in extra_fields dictionary."
+            )
+            self.extra_fields.update(extra_fields)
 
     def __len__(self) -> int:
         return len(self.items)
@@ -29,6 +49,16 @@ def __getitem__(self, index: int) -> Item:
     def __iter__(self) -> Iterator[Item]:
         return iter(self.items)
 
+    def __contains__(self, __x: Item) -> bool:
+        return __x in self.items
+
+    def __add__(self, other: Any) -> ItemCollection:
+        if not isinstance(other, ItemCollection):
+            return NotImplemented
+
+        combined = [*self.items, *other.items]
+        return ItemCollection(items=combined)
+
     @override
     def __repr__(self) -> str:
         return f"ItemCollection({self.items})"
@@ -41,6 +71,14 @@ def to_dict(self) -> dict[str, Any]:
             **data,
         }
 
+    def clone(self) -> ItemCollection:
+        return copy.deepcopy(self)
+
+    @deprecated("Try `ItemCollection.from_dict` and handle any exceptions instead")
+    @staticmethod
+    def is_item_collection(data: dict[str, Any]) -> bool:
+        return data.get("type", "") == "FeatureCollection"
+
     @classmethod
     def try_from(cls, data: dict[str, Any] | ItemCollection) -> ItemCollection:
         if isinstance(data, ItemCollection):
@@ -53,14 +91,20 @@ def from_dict(
         cls,
         data: dict[str, Any],
         preserve_dict: bool = True,
+        root: Container | None = None,
     ) -> ItemCollection:
+        if data.get("type", "") != "FeatureCollection":
+            raise STACTypeError(data, cls)
+
         if preserve_dict:
             data = copy.deepcopy(data)
 
         items = data.get("features", [])
         extra_fields = {k: v for k, v in data.items() if k not in ("features", "type")}
 
-        return cls(items=[Item.from_dict(item) for item in items], **extra_fields)
+        return cls(
+            items=[Item.from_dict(item, root=root) for item in items], **extra_fields
+        )
 
     @classmethod
     def from_file(
diff --git a/tests/v1/test_item_collection.py b/tests/v1/test_item_collection.py
index 28af1c9e6..4b4c73bcb 100644
--- a/tests/v1/test_item_collection.py
+++ b/tests/v1/test_item_collection.py
@@ -4,13 +4,17 @@
 from typing import Any, cast
 
 import pytest
+from unittest.mock import Mock
 
 import pystac
 from pystac import Item, StacIO
 from pystac.item_collection import ItemCollection
+from pystac.reader import DEFAULT_READER
 
 from .utils import TestCases
-from .utils.stac_io_mock import MockDefaultStacIO
+
+
+pytestmark = pytest.mark.passing_v2
 
 SIMPLE_ITEM = TestCases.get_path("data-files/examples/1.0.0-RC1/simple-item.json")
 CORE_ITEM = TestCases.get_path("data-files/examples/1.0.0-RC1/core-item.json")
@@ -20,6 +24,16 @@
     "data-files/item-collection/sample-item-collection.json"
 )
 
+class MockReader:
+    mock: Mock
+
+    def __init__(self) -> None:
+        self.mock = Mock()
+
+    def get_json(self, href: str) -> dict[str, Any]:
+        self.mock.read_json(href)
+        return DEFAULT_READER.get_json(href)
+
 
 @pytest.fixture
 def item_collection_dict() -> dict[str, Any]:
@@ -199,9 +213,8 @@ def test_from_dict_sets_root(item_collection_dict: dict[str, Any]) -> None:
 
 
 def test_to_dict_does_not_read_root_link_of_items() -> None:
-    with MockDefaultStacIO() as mock_stac_io:
-        item_collection = pystac.ItemCollection.from_file(ITEM_COLLECTION)
-
-        item_collection.to_dict()
+    mock_reader = MockReader()
+    item_collection = ItemCollection.from_file(ITEM_COLLECTION, reader=mock_reader)
+    item_collection.to_dict()
 
-        assert mock_stac_io.mock.read_text.call_count == 1
+    assert mock_reader.mock.read_json.call_count == 1