diff --git a/.flake8 b/.flake8
index bb31e22..1d1c7f5 100644
--- a/.flake8
+++ b/.flake8
@@ -1,4 +1,8 @@
 # vim: ft=cfg
 [flake8]
-inline-quotes = double
 max-complexity = 7
+docstring-convention=google
+
+# Required to be compatible with black
+extend-ignore = E203,W503
+inline-quotes = double
diff --git a/app/__init__.py b/app/__init__.py
index e69de29..5927fab 100644
--- a/app/__init__.py
+++ b/app/__init__.py
@@ -0,0 +1 @@
+"""Module containing all app code."""
diff --git a/app/__main__.py b/app/__main__.py
index fec66e1..aaf2942 100644
--- a/app/__main__.py
+++ b/app/__main__.py
@@ -1,13 +1,13 @@
 """The main entrypoint of the program."""
+
+
 import argparse
 import sys
 from parser import read_specs_file
 
 
-# This just displays the error type and message, not the stack trace
 def except_hook(ext_type, value, traceback):
-    """
-    Make errors not show the stracktrace to stdout.
+    """Make errors not show the stracktrace to stdout.
 
     Todo:
         * Replace this with proper error handling
@@ -59,9 +59,9 @@ if __name__ == "__main__":
         print(json.dumps([spec.to_dict() for spec in specs], indent=4))
 
     elif not specs:
-            # TODO replace this with error handling system
-            print("No specs, exiting.")
-            sys.exit(0)
+        # TODO replace this with error handling system
+        print("No specs, exiting.")
+        sys.exit(0)
 
         for spec in specs:
             spec.backup()
diff --git a/app/notifier.py b/app/notifier.py
index 1848775..99b3ffa 100644
--- a/app/notifier.py
+++ b/app/notifier.py
@@ -1,9 +1,14 @@
+"""Module handling IFTTT notifications."""
+
+
 from typing import List
 import os
 import requests
 
 
 class Notifier:
+    """A notifier object that can send IFTTT notifications."""
+
     # (positive, negative)
     _EVENTS = {
         "backup": (
@@ -15,24 +20,40 @@ class Notifier:
             "Couldn't restore {name}.",
         ),
     }
+    """The message content for a given event."""
 
     # Placeholder
     def __init__(
         self, title: str, events: List[str], endpoint: str, api_key: str = None
     ):
+        """Initialize a new Notifier object.
+
+        Args:
+            title: the notification title to use
+            events: the event types that should trigger a notification (should
+                be one of the keys in _EVENTS).
+            endpoint: IFTTT endpoint name
+            api_key: your IFTTT API key. If not provided, it will be read from
+                the IFTTT_API_KEY environment variable.
+
+        Todo:
+            * Read the API key on init
+        """
         self.title = title
         self.events = events
         self.endpoint = endpoint
         self.api_key = api_key
 
     def notify(self, category: str, name: str, status_code: int):
-        """
+        """Send an IFTTT notification.
+
         Args:
-            category: type of notify (e.g. backup or restore)
+            category: type of notify (should be one of the keys in _EVENTS).
+                Only if the category was passed during initialization will the
+                notification be sent.
             name: name of the spec
             status_code: exit code of the command
         """
-
         event = "{}_{}".format(
             category, "success" if status_code == 0 else "failure"
         )
diff --git a/app/parser.py b/app/parser.py
index dcd9fb1..ce5fdf5 100644
--- a/app/parser.py
+++ b/app/parser.py
@@ -1,4 +1,6 @@
 """Handles parsing a config file from disk."""
+
+
 import yaml
 from pathlib import Path
 from typing import List, Union
@@ -7,8 +9,7 @@ import skeleton
 
 
 def read_specs_file(path: Union[str, Path]) -> List[Spec]:
-    """
-    Read a config file and merge it with the skeleton.
+    """Read a config file and merge it with the skeleton.
 
     Args:
         path: path to the yaml config file
diff --git a/app/skeleton.py b/app/skeleton.py
index 5391e1b..b1aabd3 100644
--- a/app/skeleton.py
+++ b/app/skeleton.py
@@ -6,8 +6,7 @@ class InvalidKeyError(Exception):
     """Thrown when a config file contains an invalid key."""
 
     def __init__(self, key: str):
-        """
-        Create a new InvalidKeyError object with the given key.
+        """Create a new InvalidKeyError object with the given key.
 
         Args:
             key: the invalid key
@@ -21,8 +20,7 @@ class MissingKeyError(Exception):
     """Thrown when a required key is missing from a config."""
 
     def __init__(self, key: str):
-        """
-        Create a new MissingKeyError object with the given key.
+        """Create a new MissingKeyError object with the given key.
 
         Args:
             key: the invalid key
@@ -33,8 +31,7 @@ class MissingKeyError(Exception):
 
 
 def merge(*dicts: [Dict]) -> Dict:
-    """
-    Merge multiple dicts into one.
+    """Merge multiple dicts into one.
 
     It reads the dicts from left to right, always preferring the "right"
     dictionary's values. Therefore, the dictionaries should be sorted from
@@ -78,8 +75,7 @@ def merge(*dicts: [Dict]) -> Dict:
 
 
 def merge_with_skeleton(data: Dict, skel: Dict) -> Dict:
-    """
-    Merge a dictionary with a skeleton containing default values.
+    """Merge a dictionary with a skeleton containing default values.
 
     The skeleton not only defines what the default values are, but also
     enforces a certain shape. This allows us to define a config file using a
diff --git a/app/specs/container.py b/app/specs/container.py
index 76579f0..7bc2a95 100644
--- a/app/specs/container.py
+++ b/app/specs/container.py
@@ -1,4 +1,4 @@
-"""Module defining a Container-based spec."""
+"""Module defining a container-based spec."""
 from .spec import Spec
 from typing import Union
 from pathlib import Path
@@ -46,6 +46,7 @@ class ContainerSpec(Spec):
         self.command = command
 
     def backup(self):
+        """Create a new backup."""
         # Remove excess backups
         self.remove_backups()
 
diff --git a/app/specs/directory.py b/app/specs/directory.py
index 4fa0ffe..17048a7 100644
--- a/app/specs/directory.py
+++ b/app/specs/directory.py
@@ -1,3 +1,6 @@
+"""Module defining a directory-based spec."""
+
+
 from .spec import Spec
 from pathlib import Path
 from typing import Union
@@ -23,6 +26,18 @@ class DirectorySpec(Spec):
         extension: str,
         notify=None,
     ):
+        """
+        Initialize a new DirectorySpec object.
+
+        Args:
+            name: name of the spec
+            source: what directory to back up
+            destination: where to store the backup
+            limit: how many backups to keep
+            command: what command to use to create the backup
+            extension: extension of the backup files
+            notify: a Notifier object that handles sending notifications
+        """
         super().__init__(name, destination, limit, extension, notify)
 
         self.source = source if type(source) == Path else Path(source)
@@ -36,6 +51,7 @@ class DirectorySpec(Spec):
         self.command = command
 
     def backup(self):
+        """Create a new backup."""
         # Remove excess backups
         self.remove_backups()
 
diff --git a/app/specs/spec.py b/app/specs/spec.py
index 2669ccb..d5e0b26 100644
--- a/app/specs/spec.py
+++ b/app/specs/spec.py
@@ -1,3 +1,6 @@
+"""This module contains the base Spec class."""
+
+
 from pathlib import Path
 from typing import Union, Dict
 import skeleton
@@ -7,9 +10,7 @@ import inspect
 
 
 class Spec:
-    """
-    Base class for all other spec types.
-    """
+    """Base class for all other spec types."""
 
     _SKEL = {
         "destination": None,
@@ -31,23 +32,25 @@ class Spec:
         extension: str,
         notify=None,
     ):
-        """
+        """Initialize a new Spec object.
+
+        This initializer usually gets called by a subclass's init instead of
+        directly.
+
         Args:
             name: name of the spec
             destination: directory where the backups shall reside
             limit: max amount of backups
             notifier: notifier object
         """
-
         self.name = name
-        self.destination = (
-            destination if type(destination) == Path else Path(destination)
-        )
+        self.destination = Path(destination)
 
         # Create destination if non-existent
         try:
             self.destination.mkdir(parents=True, exist_ok=True)
 
+        # TODO just make this some checks in advance
         except FileExistsError:
             raise NotADirectoryError(
                 "{} already exists, but isn't a directory.".format(
@@ -61,8 +64,7 @@ class Spec:
 
     @classmethod
     def skeleton(cls: "Spec") -> Dict:
-        """
-        Return the skeleton for the given class.
+        """Return the skeleton for the given class.
 
         It works by inspecting the inheritance tree and merging the skeleton
         for each of the parents.
@@ -78,10 +80,7 @@ class Spec:
         )
 
     def remove_backups(self):
-        """
-        Remove all backups exceeding the limit
-        """
-
+        """Remove all backups exceeding the limit."""
         files = sorted(
             self.destination.glob("*." + self.extension),
             key=os.path.getmtime,
@@ -93,13 +92,22 @@ class Spec:
                 path.unlink()
 
     def backup(self):
+        """Create a new backup.
+
+        This function should be implemented by the subclasses.
+        """
         raise NotImplementedError()
 
     def restore(self):
+        """Restore a given backup (NOT IMPLEMENTED).
+
+        This function should be implemented by the subclasses.
+        """
         raise NotImplementedError()
 
     @classmethod
     def from_dict(cls, name, obj: Dict, defaults: Dict) -> "Spec":
+        """Create the class given a dictionary (e.g. from a config)."""
         # Combine defaults with skeleton, creating new skeleton
         skel = skeleton.merge(cls.skeleton(), defaults)
 
@@ -109,4 +117,7 @@ class Spec:
         return cls(name, **obj)
 
     def to_dict(self):
+        """Export the class as a dictionary.
+
+        This function should be imnplemented by the subclasses."""
         raise NotImplementedError()
diff --git a/app/specs/volume.py b/app/specs/volume.py
index cd9d937..f6f0980 100644
--- a/app/specs/volume.py
+++ b/app/specs/volume.py
@@ -6,9 +6,7 @@ import subprocess
 
 
 class VolumeSpec(Spec):
-    """
-    A spec for backing up a Docker volume.
-    """
+    """A spec for backing up a Docker volume."""
 
     _SKEL = {
         "volume": None,