Just finished this book, it is very good, and I highly recommend it. I can't improve on Eva's comments.
Copyright 1948, about 370 pages with lots of footnotes. Herndon was quite a character, and I found the parts about how he went about researching and writing his book to be very interesting. It is an excellent companion book to "Herndon's Lincoln" and Herndon's Informants"
It is available online
https://archive.org/details/lincolnsherndon007410mbp
An inexpensive hardback copy is available. A new softbound is under $10
http://www.amazon.com/Lincolns-Herndon-D...1437222194
This page and a half, from the epilogue of the book, will help give you a better idea on the content.
https://archive.org/stream/lincolnshernd...6/mode/1up