Runes were unlike normal letters that everyone was used to. They have power and from untrained eyes, they will look the same to a degree.
One need to know them to spot the difference and even used them. Just like now, Eugene only know Rune Of Summon because that knowledge was inserted inside his mind in completion.
Wherever he saw it, he will recognised it. But any other runes were just the same to him. He had to look and feel them.
You don't read runes, you feel them, then read them, then comprehend them. If that happened then even with eyes close, a rune close to you will appear like a spark.
However, learning wasn't easy. Even with Mystery Door that gave Eugene access to many runes to explore. It will take him decade to understand them at basic level let alone use them.
