The Gospel of John is a great book of the Bible, and I don’t want to minimize that. It has some great passages, such as 3:16. That said, it is important to realize that it speaks a very different message to the unsaved person.
Before I got saved, I had two different people recommend that I read the Gospel of John, the Gospel of Love, as my first book of the Bible. When I was a staunch atheist, this was actually a very bad idea! As an atheist, I interpreted what Jesus was saying as evidence that he was arrogant, not humble. The overtones of the mystical also had a negative impact on me.
The problem, of course, is that I didn’t have any commentary to go with it. Unfortunately, an atheist is likely to buy the cheapest Bible available, which goes pretty light on introductions. Worse, I didn’t read any of the other Gospels. They have a much more down-to-earth feel that would have made them much easier to digest, even if they might not speak to a Christian as loudly.
The key I was missing, and that many unsaved people will miss, is that John was written to… the Greeks. John is the Gospel written to philosophers to explain who Jesus was in their terms. Of course, their terms are no longer our terms, and the result is a Gospel that feels very bizarre, even after you have the Holy Spirit guiding you through it.
We don’t have the concept of the Logos (Word) as a creative force that holds things together, though Christians have this concept for Jesus. When Jesus speaks, forcefully, of eating his flesh and drinking his blood as the mechanism of salvation, it forces the reader to either dig deeper or recoil in disgust. When Jesus speaks of being born again, the unchurched modern reader will be understandably confused. The fact that the unsaved reader then reads of people having his exact same reaction just makes it harder. The Gospel of John, more than any other, makes it easy for a reader to conclude that Jesus was a kook!
Does this mean I don’t think you should read John? No! It means you should practice reading the Bible with an eye, not just for what the Spirit speaks to you through it, but also for what Satan might try to speak through it. When I was an atheist, I read the Gospel of John, and became more secure in my atheism! My attitude towards Jesus became more negative. I changed from being open to hearing the gospel, to closed.
For me, as a mathematician, Luke probably would have worked better. It’s a simple recording of the facts of Jesus’ life. Had I then skipped over John into Acts, I could have gotten a matter-of-fact reading of who Jesus was, what he had done, and what his impact had been. After reading John, I wasn’t interested in reading Acts.
Know your audience, and know your Bible. Some well-meaning people were stumbling blocks to me, because they didn’t understand how I would read John.