You should actually read it.
To me, the main point is that the existence of “Real Lincoln” in itself balances out all the fawning praise of the man. I don’t think there’s 1 book ever written about Lincoln that’s ever been really critical of him. It’s all been worshipful praise. “RL” provides the balance.
That's like saying Rosie O'Donnell balances out all the supporters of the U.S. military. Presenting a completely unbalanced portrait of Lincoln as a balancing factor is dishonest.