You can see the similarities shared among the synoptic gospels of Matthew, Mark and Luke below:
On the other hand, only about 8% of the gospel of John parallels the other Gospels. While the laity tend to favor John, scholars often give it a hard time for being so different.
I recently watched this video over at the Huffington Post with Peter Kreeft, Philip Jenkins, Peter Lillback and Reza Aslan. Aslan is one of the scholars that sees John as being different because the story of Jesus evolved, and the author was crafting the story to support the theological views of the time.
Mirror-reading takes a different approach. The Gospel narratives are not simply a recording of events but a response to the situations the authors were facing at the time. It's not like Matthew, Mark, Luke or John sat down one day and said, "I think I'll write down all the things I know or believe about Jesus." They all should be viewed as half of a conversation. The Gospel of John was simply responding to a different set of circumstances than the other Gospels were. That shouldn't necessitate that we view John with suspicion, or that his narrative is any less credible. You can watch my video on mirror-reading narratives, or check out any of the narratives on the Books of the Bible page.