Inherit from abc.ABC

If we're doing nominal typing, do it correctly.

pyproject.toml

@@ -81,7 +81,7 @@ target-version = "py310"
 strict = true
 
 [tool.mypy]
-exclude = ["dist"]
+strict = true
 
 [[tool.mypy.overrides]]
 module = ["ebooklib", "ebooklib.epub", "mobi", "kindle"]

src/screener/reader/epub.py

@@ -8,7 +8,7 @@
 
 from ebooklib import epub
 
-from .abstract import AbstractReader
+from screener.reader.types import AbstractReader
 
 
 class EpubFileReader(AbstractReader):

src/screener/reader/kindle.py

@@ -9,7 +9,7 @@
 
 from mobi import extract
 
-from .abstract import AbstractReader
+from screener.reader.types import AbstractReader
 
 
 class KindleFileReader(AbstractReader):

src/screener/reader/types.py

@@ -0,0 +1,35 @@
+from __future__ import annotations
+
+import abc
+import typing
+
+if typing.TYPE_CHECKING:
+    from pathlib import Path
+    from types import TracebackType
+
+
+class AbstractReader(abc.ABC):
+    def __init__(self: AbstractReader, file_path: Path) -> None:
+        self.file_path = file_path
+
+    @abc.abstractmethod
+    def __enter__(self: AbstractReader) -> AbstractReader: ...
+
+    @typing.overload
+    def __exit__(self, exc_type: None, exc_val: None, exc_tb: None) -> None: ...
+
+    @typing.overload
+    def __exit__(
+        self,
+        exc_type: type[BaseException],
+        exc_val: BaseException,
+        exc_tb: TracebackType,
+    ) -> None: ...
+
+    @abc.abstractmethod
+    def __exit__(
+        self: AbstractReader,
+        exc_type: type[BaseException] | None,
+        exc_val: BaseException | None,
+        exc_tb: TracebackType | None,
+    ) -> None: ...