I downloaded several of these free compilations of Lincoln's writings and have found them to be fascinating views into what Lincoln actually said and believed.
Just as one example, Lincoln's comments about liquor's effects on people in his day and his firm support for prohibition way back in the mid 1800s are eloquently stated and made me think that Ken Burns could have benefited from reading Lincoln's discussion of these issues before he made his recent PBS series on the subject.
I highly recommend taking advantage of the various free books available for the kindle as well as the many inexpensive downloadable volumes. Kindle reader programs are also available for use with Macs, PCs, and various of the tablet computers.