Quick notes on Mark
Whatever the finer structure of the book may be, Mark has a teeter-totter structure: it begins on the run, works its way up to Peter’s confession of Jesus as the Christ in ch. 8, and then runs downhill from there to the empty tomb in ch. 16. Another way of putting it is this: the first half answers the question Who is Jesus? (yes, this is answered at the very start, but that is the case for the reader/hearer and not those there with Jesus), while the second focuses on the question What does it mean for Jesus to be the messiah? (which is kicked off nicely by Peter when he rebukes Jesus for telling them exactly what it means for him to be the messiah). The ending at 16.8 is consonant with the focus of the second half of the book, and drives the reader/hearer of Mark back to the beginning.
The Pharisees’ request for a sign in ch. 8 comes after Jesus had been giving sign after sign. No wonder he, as the ESV has it, “sighed deeply in his spirit”.
The eschatology of ch. 13 is right in line with the presentation of Mark; just as Jesus just shows up at the beginning of the book, and hits the ground running, so too will his return be swift and unexpected (except for those to whom he speaks, who should know the signs & be ready, as Israel ought to have been ready for the messiah’s arrival after John appeared in the wilderness).
Mark carefully names and identifies Jesus’ followers, whether disciples or in the larger group. These are in many cases people the writer may expect his audience would know by name (see 3:13-21; 13:46; 15.21; 15.40-41).