Haskell Types

So I've been learning Haskell for some time, I get some basic and intermediate stuff, some monad basics, but could anyone recommend a good tutorial that explains type system better than YAHT?

module Main
    where

import IO

getNums = do
  putStrLn "give numbers"
  number <- getLine
  if number == "0"
     then return []
     else do
       rest <- getNums
       let final = (number : rest)
        in return final

How do I make it return list of factorials of final? What I thought about was mapping read across final, then mapping fact on the list of numbers, but it doesn't work.