I think I've always preferred the other Gospels to Mark -- what kind of a Gospel doesn't include a birth narrative?? -- and wondered what was uniquely valuable about Mark. If the bulk of the material also appears in Matthew or Luke, what does Mark have to offer? And why is it sandwiched between its two, completer sisters instead of coming first in order? Wouldn't it be better to get Mark over with so that we can delve into the meatier Gospels?
Wrestling with these questions while reading the book, I was able to develop some answers that satisfy me. Compared to Matthew, Mark is a breathtakingly elegant book -- much shorter, much more streamlined, less context and less attention given to plot. It feels like breathing cool, crisp air that takes you aback in its coolness and crispness. Matthew, writing (I believe) more specifically for a Jewish audience, adds the nativity account, the genealogy, and a constant attention to Jesus' reception among the Jews (so that we learn how almost every miracle and teaching was received by the crowds or the Pharisees or the disciples or some combination of those audiences). In Matthew, the literary plot of audience reaction turns into the enemies' plot to convict and execute Jesus; Mark doesn't draw together the events, from the beginning to the end of the book, so tidily -- the book is much less plot-driven. So in Mark, the teachings of Christ seem to rise and float above the narrative. Same teachings, very different effect.
The sequence of the Gospels ended up striking me an ideal ordering, because Mark comes as a sort of breather between Matthew and Luke -- the smaller, lighter read that you reach for between two epic, intense books. (And I mean that in the most approving way: there is nothing inherently more laudable about a book being "intense" rather than "light," provided each is a worthy book; each type has its value and its own literary excellences.) If Matthew and Luke are similar for certain reasons and Mark and John dissimilar for other reasons, it's both intellectually pleasing and a gift to the reader to get a sort of quatrain (ABAB) in the ordering of the Gospels.