The author mentions how the race question was never quite solved.

Question: Where did Lincoln fall short in his policies?

Foner:    There was a tendency in the Lincoln literature, unfortunately, to sort of take Lincoln as the perfect model, and therefore, anyone who criticized him must be off base.  I respect Lincoln enormously.  I also respect the abolitionists who criticized him at the beginning of the war for not taking action directly against slavery early on.  It was their pressure that forced him to move more quickly than he wanted against slavery.  So, you know, the fact that he waited two years or a year and a half should not make us just think, well, that was the only way to do it.  I think that he was too slow.  He was certainly too slow in being willing to enlist black soldiers.  Lincoln wanted to keep slavery off the political agenda for a good while in the war, and I think that was an error.  I think the abolitionists and the radical Republicans and slaves themselves understood, right at the beginning, this war is caused by slavery, and you’re never going to win this war unless you attack slavery.  So, you know, Lincoln’s timing was open to criticism, and I think he waited too long.  And then, again, Lincoln…  Now, Lincoln always said, “I’ve got to wait ‘til public opinion comes along.  I can’t go too far ahead of it.”  On the other hand, the president needs public opinion and forms and shapes public opinion, so Lincoln might have done more during the war but, you know, this is all speculation.  We don’t know what might have happened if Lincoln had taken different policies.