Academy for the Fallen, Year One by Avery Song

I lived, fought, and died in the battle between good and evil.
But not as a hero…
After falling in battle, Lilith, known as Queen Merciless to foe and friend alike, expects to wake up in the toasty halls of hell —not the depths of the Underworld as a candidate for entry into the Academy for the Fallen.
Confused, she assumes it’s either a misunderstanding or someone’s idea of a joke. Forced to prove her strength with three challenging tests, Lilith is determined to dominate, showing she has no need for more schooling.
She’s no damsel needing protection or rescue.
Stuck with a former angel on the outs with God, a hellhound with a dangerous secret, and a trickster shapeshifter posing as the previous King of the Afterlife, Lilith thinks they should change the school’s name to Academy for Psychos.
Her opinion only strengthens when she meets the dastardly sexy headmaster.
There are no math classes. No one cares what books you read. And the only chemistry that matters is deadly.
Academy for the Fallen has no use for the weak and pure. Its purpose is to train an elite force of the evilest, blood diven souls to keep the Damned from escaping Satan’s grasp and unleashing hell on Earth.
Time for Lilith to dust off her crown and fight alongside the irresistible dark trio determined to win her affection.
There’s a new war to wage — the battle between evil and evil — and no one is a badder bitch than Queen Merciless.