Being in the midst of Sunday School season such as we are, I've found myself fielding a lot of "Where is ____ in the Bible?" or "What book did Jesus do ____ in?" Truth be told, I do not recall where everything occurs in the Bible...but that's what concordances (or, let's be realistic here, Google) are for. However, I do know a thing or two about HOW to read the Bible, what to look for, and what points the ancient authors were trying to make. So, here are a few overviews to help us be better Bible navigators.
Matthew: Matthew is the "Jewish-y" gospel. It is geographically very familiar with Ancient Palestine. Since the gospel of Matthew is so Jewish in character and flavor, it serves as a good bridge with the Old Testament, and is thus the first book of the New Testament. The book rips on the Jewish leadership of Jesus' day a great deal. Jesus takes them to task several times, however this has historically led Christians to some awkward conclusions, such as a tendency to want to exonerate Pilate a bit and pin all the blame on the Jews. In short, Matthew uses the Old Testament a great deal, and chances are, if you are looking for a text that uses Isaiah to foretell of Jesus...it's in Matthew.
Mark: Though Mark is the 2nd Gospel, it is almost certainly the earliest gospel to have actually been written down. Mark is the attention-deficit gospel: it is the shortest gospel, and it is full of concrete bits and stories joined together with "and" or "and immediately". Some scholars think Mark is actually a more-or-less complete retelling of an oral tradition of Christ. Jesus is forever moving and doing stuff in Mark. Mark often puts a different story right smack in the middle of a larger story...which calls attention to certain aspects of the story well, and forces us to re-read things to get a clearer picture of what is going on. Mark doesn't have time for reflection and theological theorizing; Mark even has a very brief account of Jesus' resurrection, which later writer's felt the need to add on to so as to better match Matthew and Luke (the other 2 synoptic gospels). If you want a 1-2 hour account of what Jesus was all about, Mark is the way to go.
Luke: This book is akin to Matthew, but less Jewish. The author of the gospel is familiar with Judaism, but does not lean on Jewish tradition in the same way Matthew does, and the author is prone to using awkward terms when telling of places Jesus went and did things; he makes the rural villages of Palestine seem too urban for the context. However, Luke is a master of style, and the gospel has great appeal to an audience of varied background or ethnicity. Since Luke focuses a great deal on Christ's compassion...his care for the poor and healing of the sick...Luke is a very appealing gospel that is easy to relate to. Luke is also a companion piece to Acts (written by the same author, or at least put together by the same editor), and the same emphases can be glimpsed in that work. This broad appeal, coupled with the fact that Luke tells us up front (Luke 1:1-4) that he scoured all the accounts of Christ he could get his hands on to make a logical retelling of the good news (he used source material) leads me to view Luke as the modern, thinking (wo)man's gospel.
John: This gospel is weird, brilliant, and beautiful. John is so different from the other gospels, that it is referred to differently; the others are collectively known as the synoptic gospels, while John is a beast unto it's own. For starters, the gospel of John does not have Jesus telling any parables...a characteristic teaching style apparently employed by him. Where as in the other gospels Jesus goes to Jerusalem only once, late in his ministry, in John, Jesus goes to Jerusalem several times. Conversely, on his last visit to Jerusalem, John does retell the last supper, but it is a bit different than the other accounts, and most notably is not a Passover meal, and does not feature an institution of the Eucharist. John is DEEP however: it portrays Jesus as a revealer...he often uses words with a double-meaning, and many who should grasp what Jesus is getting at can't, such as Nicodemus. John has more theological development and reflection than the other gospels, and in general tends to read like a monologue of a wizened old man (see John 3:16 for example). What's more, there is compelling literary/contextual evidence that John was actually written by Lazarus of Bethany, one of Jesus' closest friends outside the disciples, which adds quite an interesting wrinkle when considering this gospel. If your looking for a gospel that your brain can chew on, John is the one you want.