walaikum as salaam wa rahmatullahi wa barakaatuhu,
ukty,
the reward for memorizing them is entering jannah.the prophet (saw.)said.
Allah has 99 names,whoever knows them by heart enters Paradise.
You should know that the scholars say it not only means memorizing them,but acting upon them.You may ask "how do we act upon them?"example;Allah is AlGhafoor.,The Forgiver,so we ask Allah for forgiveness when we sin and we also forgive others so that He will forgive us.
Baarakallahu feeki