what's wrong with:

```haskell
instance FromJSON SimpleTransaction where
    parseJSON (Object o) = SimpleTransaction <$> o .:  "account"
                                             <*> o .:? "address"
                                             <*> o .:  "category"
                                             <*> o .:? "fee"
                                             <*> o .:  "amount"
                                             <*> o .:? "confirmations"
                                             <*> o .:? "blockhash"
                                             <*> (fromIntegral <$>  o .:? "blockindex")
                                             <*> o .:? "blocktime"
                                             <*> o .:? "txid"
                                             <*> o .:? "walletconflicts"
                                             <*> (fromIntegral <$>  o .: "time")
                                             <*> (fromIntegral <$>  o .:? "timereceived") 
                                             <*> o .:? "comment"
                                             <*> o .:? "to"
                                             <*> o .:? "otheraccount"
```
?