He is the author of
The World That the Shooter Left Us (Four Way Books, 2022);
More Than Watchmen at Daybreak (Nine Mile Books, 2020);
The Gospel According to Wild Indigo (Southern Illinois University Press, 2018);
The Crossed-Out Swastika (Copper Canyon Press, 2012);
More Than Peace and Cypresses (Copper Canyon Press, 2004);
Beautiful Signor (Copper Canyon Press, 1997), which won the Lambda Literary Award;
Soul Make a Path Through Shouting (Copper Canyon Press, 1994), which was nominated for the Pulitzer Prize and received the William Carlos Williams Award; and
The Mud Actor (Henry, Holt & Co., 1982), which was a National Poetry Series selection.
Cassells is the recipient of a 1995 Pushcart Prize, the Peter I.B. Lavan Younger Poets Award, and fellowships from the Lannan Foundation, the Rockefeller Foundation, and the National Endowment for the Arts. He has worked as a translator, film critic, actor, and teacher.