Death Frost Dumb

I ran a session of Death Frost Doom last Sunday and the highest Intelligence score amongst any of the PCs was only a 5. Which meant that many parts of the module were indecipherable to the characters, since they couldn't read. They didn't find half of the stuff that they could have found, and what they did get access to still left one of them dead and one of them almost dead. It was still a creepy adventure for them.