The book Heart of darkness bound with one of conrad's other works the secret sharer and they have about equal pages with about 90-ish pages per book
She Is the Darkness has 470 pages.
A Darkness at Sethanon has 425 pages.
Stalking Darkness has 512 pages.
A Handful of Darkness has 224 pages.
The Lake of Darkness has 201 pages.
Dwellers in Darkness has 203 pages.
Chasing Darkness has 288 pages.
Time of our Darkness has 328 pages.
At the Gates of Darkness has 322 pages.
Green Darkness has 480 pages.
Blooms of Darkness has 265 pages.
Swallowing Darkness has 384 pages.