H.P. Lovecraft's The Call of Cthulhu for Beginning Readers

After the death of his great-uncle, Francis Wayland Thurston delves into the late Profesor Angell's effects... 

I was sorting through
all his research one day,
when I found a monstrosity
made out of clay.

Spurred on by his curiosity, Francis learns of many terrible things. The artist who came to his uncle for help. A raid in the Louisiana swamps, led by Inspector Legrasse. The sailor Gustaf Johansen. And, perhaps most importantly, the horrible fate of the Emma.