The spine of this book says “The Journal of Alton Turner Blackwood” in reference to the story.

From CharnelHouse.com:
“Only the Charnel House Limited Edition includes the related novella Darkness Under the Sun (otherwise available as an E-book release).This book is partially told in hand written journal entries and is appropriately designed as The Journal of Alton Turner Blackwood. Journal entries are typeset in script and printed in sepia-tone. This oversize 474 page edition is exquisitely printed in two colors on luxurious Beige Mohawk Superfine and Frankfurt Cream. Both editions are bound by hand and foil stamped in 22kt gold. All books are hand signed by the author in sepia-tone ink.”

With the later release of the premium paperback edition of What the Night Knows the statement that this is the only edition to contain both texts is inaccurate.