diff --git a/src/Data/String/Builder.hs b/src/Data/String/Builder.hs
--- a/src/Data/String/Builder.hs
+++ b/src/Data/String/Builder.hs
@@ -1,7 +1,7 @@
-{-# LANGUAGE GeneralizedNewtypeDeriving, GADTs #-}
+{-# LANGUAGE GADTs #-}
 -- |
--- `build` can be used to construct multi-line string literals in a monadic
--- way.
+-- The `build` function can be used to construct multi-line string literals in
+-- a monadic way:
 --
 -- > {-# LANGUAGE OverloadedStrings #-}
 -- >
@@ -12,23 +12,34 @@
 -- >   "foo"
 -- >   "bar"
 -- >   "baz"
---
--- `return` and `>>=` are not useful in this context!
-module Data.String.Builder (build, Builder, BuilderM) where
+module Data.String.Builder (
+-- * Functions
+  build
+, literal
+-- * Types
+, Builder
+, BuilderM
+) where
 
 import Data.String
-import Control.Monad.Trans.Writer
 
-newtype BuilderM a = BuilderM { runBuilderM :: Writer String a }
-  deriving Monad
+-- | A writer monad for string literals.
+data BuilderM a = BuilderM a ShowS
 
+instance Monad BuilderM where
+  return a            = BuilderM a id
+  BuilderM a xs >>= f = case f a of
+    BuilderM b ys -> BuilderM b (xs . ys)
+
 type Builder = BuilderM ()
 
+-- | Add a literal string.
 literal :: String -> Builder
-literal = BuilderM . tell
+literal = BuilderM () . showString
 
 instance (a ~ ()) => IsString (BuilderM a) where
-  fromString s = literal s >> literal "\n" >> return ()
+  fromString s = literal s >> literal "\n"
 
+-- | Run a builder.
 build :: Builder -> String
-build = snd . runWriter . runBuilderM
+build (BuilderM () s) = s ""
diff --git a/stringbuilder.cabal b/stringbuilder.cabal
--- a/stringbuilder.cabal
+++ b/stringbuilder.cabal
@@ -1,5 +1,5 @@
 name:             stringbuilder
-version:          0.2.0
+version:          0.3.0
 synopsis:         A monadic builder for multi-line string literals
 description:      <https://github.com/sol/stringbuilder#readme>
 category:         Testing
@@ -22,7 +22,6 @@
       src
   build-depends:
       base < 5
-    , transformers
   exposed-modules:
       Data.String.Builder
 
@@ -34,9 +33,9 @@
   ghc-options:
       -Wall -Werror
   hs-source-dirs:
-      src, test
+      test
   build-depends:
       base
-    , transformers
+    , stringbuilder
     , hspec         >= 1.3
     , QuickCheck