The Sandman: Book One

That went just as dark as I feared, but there were some truly spectacular feats of imagination, and even some sweet, beautiful moments that help me understand why it's such a popular series. I honestly don't think I could competently list all the potential trigger warnings, but the length of these bound volumes encourages you to take your time, and take a break from it, which I recommend. 
Did not know before starting that this not only originated in, but thoroughly reflects the 80s, but it's a fascinating window back - not just the fashion, the drugs and the AIDS crisis, but contemplating how groundbreaking it may have been: how it not simply humanizes but takes in stride, the existence of gay people and and drag queens. It shouldn't be a big thing, but if I've got my historical timeline right, it still was.
Having attempted the American Gods graphic novels (adapted from the novel), I can say it makes a difference that this Neil Gaiman story was first shaped to accompany art; I found the American Gods series very wordy the way it was presented in graphic medium, didn't strike the same balance between text and image.