Oh, man, the read was tedious. The battle, on the Union side, was a
sequence of blunders and misfortunes, often criminal ineptitude of
union high command. So the book becomes a litany of missed
opportunities. Sears even counts them towards the end of the book: six
opportunities for McClellan to crush Lee. He mentions the last one, on
the day following the battle (the army of northern virgina had no
reserves and had been bled dry) to launch an offensive and destroy
the Confederacy. So, Sears just mentions that this missed opportunity
is no better or worse than the other five major ones. 

Courage and heroism of the rank-and-file and field commanders on both
sides was in abundance. Yet, the battle as a whole is constant
repetition of missed opportunities, tremendous loss of life and little
to show for it.

None of this Sears' fault. It is just difficult to construct a
relatable narrative out of the whole battle. I was thinking Antietam
may be described from the confederate's standpoint: fighting to a draw
against overwhelming odds.