The question isn't, do you know about Him? It is - do you know Him? Many who call themselves Christians know about Him. But they don't know Him. Knowing about someone and knowing someone are two entirely different things. Knowing about someone is based on things you heard about the person. Perhaps things you read about them. It might also be based on another person's experience with an individual. You know how it works. You hear something about someone. You read something printed about someone or another person tells you about a situation they had with an individual and without even knowing this person, we form an opinion about them without knowing this person at all. We even tell others what we heard, read, or what someone else has told us like it is the absolute truth. This not only happens with situations and individuals.
It also happens with God. Most of what we know about God doesn't come from having a personal relationship with Him. It's based on what someone else has said. It's based on what someone else has read. It is based on someone elses experience. Its very rarely based on our own personal relationship with Him. We are to have our own personal relationship with Him, so when we hear something about Him that isn't true, we know it isn't true. When we read something about Him that isn't so we will know it and when someone tells us something about Him, we will be able to determine if it is accurate or not, because we know Him.
Jesus told those that said to Him that they prophesied, cast out devils, and even did wondrous works in His Name, "Depart from me. I never knew you". This further proves just because you do things like prophesy, cast out devils, and you even do wondrous works doesn't mean you know Him. Jesus Himself said it. Jesus was actually saying "Depart from me, I never had an intimate relationship with you" (John 7:22-23).
We need to have an intimate relationship with Him. We need to know Him and the power of His resurrection (Philippians 3:10). Jesus said, "If we don't have an intimate relationship with Him and we don't know Him and He knows us, we are workers of iniquity. Jesus was telling us that we need to be doing things for Him out of our relationship with Him, not from what someone said we should be doing. So the question is - do you know Him?