diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,12 @@
+2.1.0
+-----
+* Restored original `AsJSON` and `_JSON` typing
+* Bumped `microlens` dep max
+
 2.0.0
 -----
 * Complete conversion to `microlens`
+* All `Prism` are now `Traversal`
 
 1.0.0.5
 -------
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -35,7 +35,7 @@
 --------------------------
 -- | Optionally getting one value
 a :: Maybe Int
-a = ("37" :: Text) ^? _Integer  -- Just 42
+a = ("37" :: Text) ^? _Integer  -- Just 37
 
 -- | Setting one value within encoded JSON
 b :: Maybe Text
@@ -49,30 +49,44 @@
 c = "[1, 2, 3]" ^.. values  -- [Number 1.0, Number 2.0, Number 3.0]
 
 -- | Get all values cast to some simpler number type.
-c :: [Double]
-c = "[1, 2, 3]" ^.. values . _Double  -- [1.0, 2.0, 3.0]
+d :: [Double]
+d = "[1, 2, 3]" ^.. values . _Double  -- [1.0, 2.0, 3.0]
 
 -- | Access a specific index, and set a `Value` directly.
-d :: Text
-d = "[1,2,3]" & nth 1 .~ Number 20  -- "[1,20,3]"
+e :: Text
+e = "[1,2,3]" & nth 1 .~ Number 20  -- "[1,20,3]"
 
 -----------------------
 -- Manipulating objects
 -----------------------
 -- | Access all values of the key/value pairs.
-e :: Text
-e = "{\"a\":4,\"b\":7}" & members . _Number %~ (*10)  -- "{\"a\":40,\"b\":70}"
+f :: Text
+f = "{\"a\":4,\"b\":7}" & members . _Number %~ (*10)  -- "{\"a\":40,\"b\":70}"
 
 -- | Access via a given key.
-f :: Maybe Value
-f = ("{\"a\": 100, \"b\": 200}" :: Text) ^? key "a"  -- Just (Number 100.0)
+g :: Maybe Value
+g = ("{\"a\": 100, \"b\": 200}" :: Text) ^? key "a"  -- Just (Number 100.0)
 
 -----------------------------------
 -- Aeson `Value`s from encoded JSON
 -----------------------------------
-g :: Maybe Text
-g = "{\"a\":4,\"b\":7}" ^? _Value
+h :: Maybe Text
+h = "{\"a\":4,\"b\":7}" ^? _Value
 -- Just (Object (fromList [("a",Number 4.0),("b",Number 7.0)]))
 ```
 
 See the Haddock documentation for a full API specification.
+
+Migration from Data.Aeson.Lens
+------------------------------
+The functions provided here are Traversals, not Prisms, therefore
+creation of encoded JSON from Haskell types like:
+
+```haskell
+>>> _Bool # True :: String
+"true"
+```
+
+is no longer possible. Otherwise, if your use cases are strictly like
+those listed in the Usage section above, then you need only to switch
+the import from `Data.Aeson.Lens` to `Lens.Micro.Aeson`.
diff --git a/lens-aeson.png b/lens-aeson.png
new file mode 100644
Binary files /dev/null and b/lens-aeson.png differ
diff --git a/microlens-aeson.cabal b/microlens-aeson.cabal
--- a/microlens-aeson.cabal
+++ b/microlens-aeson.cabal
@@ -1,6 +1,6 @@
 name:          microlens-aeson
 category:      Numeric
-version:       2.0.0
+version:       2.1.0
 license:       MIT
 cabal-version: >= 1.8
 license-file:  LICENSE
@@ -18,12 +18,14 @@
 description:   Law-abiding lenses for Aeson, using microlens.
 
 extra-source-files:
-  .travis.yml
-  .ghci
-  .gitignore
-  AUTHORS.md
-  README.md
-  CHANGELOG.md
+                   .travis.yml
+                   .ghci
+                   .gitignore
+                   AUTHORS.md
+                   README.md
+                   CHANGELOG.md
+                   microlens-aeson.png
+                   lens-aeson.png
 
 source-repository head
   type: git
@@ -40,7 +42,7 @@
                 , attoparsec           >= 0.10      && < 0.14
                 , base                 >= 4.5       && < 5
                 , bytestring           >= 0.9       && < 0.11
-                , microlens            >= 0.3       && < 0.4
+                , microlens            >= 0.3       && < 0.5
                 , scientific           >= 0.3.2     && < 0.4
                 , text                 >= 0.11.1.10 && < 1.3
                 , unordered-containers >= 0.2.3     && < 0.3
diff --git a/microlens-aeson.png b/microlens-aeson.png
new file mode 100644
Binary files /dev/null and b/microlens-aeson.png differ
diff --git a/src/Lens/Micro/Aeson.hs b/src/Lens/Micro/Aeson.hs
--- a/src/Lens/Micro/Aeson.hs
+++ b/src/Lens/Micro/Aeson.hs
@@ -40,7 +40,6 @@
   ) where
 
 import           Data.Aeson
-import           Data.Aeson.Parser (value)
 import           Data.Attoparsec.ByteString.Lazy (maybeResult, parse)
 import qualified Data.ByteString as Strict
 import           Data.ByteString.Lazy.Char8 as Lazy hiding (putStrLn)
@@ -377,16 +376,17 @@
 class AsJSON t where
   -- | '_JSON' is a 'Traversal' from something containing JSON
   -- to something encoded in that structure.
-  _JSON :: Traversal' t Value
+  _JSON :: (FromJSON a, ToJSON a) => Traversal' t a
 
 instance AsJSON Strict.ByteString where
   _JSON = lazyUtf8 . _JSON
   {-# INLINE _JSON #-}
 
 instance AsJSON Lazy.ByteString where
-  _JSON f b = case maybeResult (parse value b) of
-    Just v -> encode <$> f v
-    _      -> pure b
+  _JSON f b = maybe (pure b) (\v' -> encode <$> f v') v
+    where v = maybeResult (parse json b) >>= \x -> case fromJSON x of
+            Success x' -> Just x'
+            _ -> Nothing
   {-# INLINE _JSON #-}
 
 instance AsJSON String where
@@ -402,29 +402,27 @@
   {-# INLINE _JSON #-}
 
 instance AsJSON Value where
-  _JSON = id
+  _JSON f v = case fromJSON v of
+    Success v' -> toJSON <$> f v'
+    _ -> pure v
   {-# INLINE _JSON #-}
 
-------------------------------------------------------------------------------
--- Some additional tests for prismhood; see https://github.com/ekmett/lens/issues/439.
-------------------------------------------------------------------------------
-
 -- $LazyByteStringTests
--- >>> ("42" :: Lazy.ByteString) ^? _JSON
+-- >>> ("42" :: Lazy.ByteString) ^? (_JSON :: Traversal' Lazy.ByteString Value)
 -- Just (Number 42.0)
 --
 -- >>> ("42" :: Lazy.ByteString) ^? _Integer
 -- Just 42
 
 -- $StrictByteStringTests
--- >>> ("42" :: Strict.ByteString) ^? _JSON
+-- >>> ("42" :: Strict.ByteString) ^? (_JSON :: Traversal' Strict.ByteString Value)
 -- Just (Number 42.0)
 --
 -- >>> ("42" :: Lazy.ByteString) ^? _Integer
 -- Just 42
 
 -- $StringTests
--- >>> ("42" :: String) ^? _JSON
+-- >>> ("42" :: String) ^? (_JSON :: Traversal' String Value)
 -- Just (Number 42.0)
 --
 -- >>> ("42" :: String) ^? _Integer