I just finished reading Testament written by Benson Bobrick about John "Webb" Baker and his service in an Illinois regiment.  

"Webb" was injured a couple of times and about 90+ letters that he wrote to family survived and were spliced among the historic rendering of specific battles and events.

It as a great read which had the entirety of the letters printed at the end of the book.

Great read.  I've just started Letters & Recollections by Robert "Rob" Lee and has many poignant letters from his father to family members...but I've only read about 9 chapters thus far.