Four Years of Fighting
Charles Coffin was a newspaper corespondent who placed himself at Meade's headquarters during the battle of Gettysburg.
He makes note of Chamberlain on page 285 - 286 and also mentions the actions of Culp's Hill on page 288.
This book is of particular interest because it was published in 1866 and offers first hand accounts.
Years later Coffin would also write, Marching to Victory