Parse binary tree from file in Haskell

I have task to write Quiz Animal game. I have to read Tree data from file (the structure of file is free). After end of game is possible to be added new data in tree(actually (Animal) to be replace by (Node (Animal) (Animal)).

My problem is that i can't parse content of "database.txt" in AnimalsTree

Example "database.txt" (this content is generated with writing before call 'New Game'):

Question "Is it fly?" (Animal "Bird") (Question "Is it swim?" (Animal "Fish") (Animal "Dog"))

EDIT This is full code:

module Main where
import System.IO
data AnimalsTree = Animal String | Question String AnimalsTree AnimalsTree deriving (Read, Show)
-- Видовете отговори на потребителя
data Answer = Yes | No

main :: IO ()
main = do root <- "database.txt"
          play (read root)
          return ()

play :: AnimalsTree -> IO AnimalsTree
play root = do putStrLn "Think of an animal, I will try to guess what it is..."
               newRoot <- play' root
               writeFile "database.txt" (show newRoot)
               playAgain <- ask "Do you want to play again?"
               case playAgain of
                   Yes -> play newRoot
                   No  -> do putStrLn "Bye!"
                             return newRoot

play' :: AnimalsTree -> IO AnimalsTree
play' question@(Question q l r) = do ans <- ask q
                                     case ans of
                                        Yes -> do y <- play' l
                                                  return $ Question q y r
                                        No  -> do n <- play' r
                                                  return $ Question q l n

play' animal@(Animal _) = do ans <- ask $ "Are you thinking of " ++ show' animal ++ "?"
                             case ans of
                                Yes -> do putStrLn "I win! :)"
                                          return animal
                                No  -> do putStrLn "I give up, you win!"
                                          getNewAnimal animal


getNewAnimal :: AnimalsTree -> IO AnimalsTree
getNewAnimal animal = do putStrLn "Please help me!"
                         putStrLn "What is name of yout animal?"
                         name <- getLine
                         let newAnimal = Animal name
                         putStrLn $ "Now please enter a question that answers yes for " ++ show' newAnimal ++ " and no for " ++ show' animal
                         question <- getLine
                         return $ Question question newAnimal animal

ask :: String -> IO Answer
ask s = do putStrLn $ s ++ " (Yes/No)"
           getAnswer

getAnswer :: IO Answer
getAnswer = do ans <- getLine
               putStrLn ""
               case ans of
                   "y" -> return Yes
                   "Y" -> return Yes
                   "yes" -> return Yes
                   "Yes" -> return Yes
                   "n" -> return No
                   "N" -> return No
                   "no" -> return No
                   "No" -> return No
                   _   -> putStrLn "This is incorect answer! Please try again with value in 'Yes' or 'No'!" >> getAnswer

show' (Animal name) = (if elem (head name) "AEIOUaeiou" then "an " else "a ") ++ name
show' (Question q _ _) = q

But I get following error:

test3.hs:10:19:
    No instance for (Read (IO AnimalsTree))
      arising from a use of ‘read’
    In a stmt of a 'do' block: root <- read "database.txt"
    In the expression:
      do { root <- read "database.txt";
           play (root);
           return () }
    In an equation for ‘main’:
        main
          = do { root <- read "database.txt";
                 play (root);
                 return () }