1. Penryn and The End of Days Trilogy by Susan Ee
It's been six weeks since angels of the apocalypse descended to demolish the modern world. Street gangs rule the day while fear and superstition rule the night. When warrior angels fly away with a helpless little girl, her seventeen-year-old sister Penryn will do anything to get her back. Anything, including making a deal with an enemy angel. Raffe is a warrior who lies broken and wingless on the street. After eons of fighting his own battles, he finds himself being rescued from a desperate situation by a half-starved teenage girl. Traveling through a dark and twisted Northern California, they have only each other to rely on for survival. Together, they journey toward the angels' stronghold in San Francisco where she'll risk everything to rescue her sister and he'll put himself at the mercy of his greatest enemies for the chance to be made whole again.
The ending is pretty incomplete. The series has one of the best hate-love relationships I have ever read, so I enjoyed this series immensely. However, the world-building and story are not half as well written as the romance. The author left many unanswered questions and plot-holes, basically resulting the book to be...sloppy. Not to add on the book was originally supposed to be a five books series, but the author cuts it back to three. Personally, my gut tells me that the author basically gave up on the series despite its popularity, which also explains the sloppy ending.
2. Shatter Me by Tahereh Mafi
I have a curse I have a gift I am a monster I'm more than human My touch is lethal My touch is power I am their weapon I will fight back Juliette hasn’t touched anyone in exactly 264 days. The last time she did, it was an accident, but The Reestablishment locked her up for murder. No one knows why Juliette’s touch is fatal. As long as she doesn’t hurt anyone else, no one really cares. The world is too busy crumbling to pieces to pay attention to a 17-year-old girl. Diseases are destroying the population, food is hard to find, birds don’t fly anymore, and the clouds are the wrong color. The Reestablishment said their way was the only way to fix things, so they threw Juliette in a cell. Now so many people are dead that the survivors are whispering war – and The Reestablishment has changed its mind. Maybe Juliette is more than a tortured soul stuffed into a poisonous body. Maybe she’s exactly what they need right now. Juliette has to make a choice: Be a weapon. Or be a warrior.
The ending of this series, very much like Angelfall, left basically everything to the imagination. This resulting the book to close up in a very sloppy note. But thankfully, it seems like the author decided to continue the series, which would be a relief(and more Warner!). But she better not give us a bittersweet ending -_-.
3. Delirium Trilogy by Lauren Oliver
In an alternate United States, love has been declared a dangerous disease, and the government forces everyone who reaches eighteen to have a procedure called the Cure. Living with her aunt, uncle, and cousins in Portland, Maine, Lena Haloway is very much looking forward to being cured and living a safe, predictable life. She watched love destroy her mother and isn't about to make the same mistake. But with ninety-five days left until her treatment, Lena meets enigmatic Alex, a boy from the "Wilds" who lives under the government's radar. What will happen if they do the unthinkable and fall in love?
The ending was probably worst than Angelfall's. It is one of the true WTF endings that leave you like this:
If you don't believe me, go to Goodreads. I'm not the only one who thinks that.
4. A Court of Thorns and Roses Series by Sarah J. Maas
Feyre's survival rests upon her ability to hunt and kill – the forest where she lives is a cold, bleak place in the long winter months. So when she spots a deer in the forest being pursued by a wolf, she cannot resist fighting it for the flesh. But to do so, she must kill the predator and killing something so precious comes at a price ... Dragged to a magical kingdom for the murder of a faerie, Feyre discovers that her captor, his face obscured by a jewelled mask, is hiding far more than his piercing green eyes would suggest. Feyre's presence at the court is closely guarded, and as she begins to learn why, her feelings for him turn from hostility to passion and the faerie lands become an even more dangerous place. Feyre must fight to break an ancient curse, or she will lose him forever.
Okay, this one was a little bit reaching. The only reason the ending to this series was even a little bit incomplete is because the series is continuing as a spin-off
5. The Black Mage Series by Rachel E. Carter
Magic. Romance. Rivals. Perfect for fans of Throne of Glass, Falling Kingdoms, and Tamora Pierce. Before the age of seventeen, the young men and women of Jerar are given a choice —pursue a trade or enroll in a trial year in one of the realm’s three war schools to study as a soldier, knight, or mage… For fifteen-year-old Ryiah, the choice has always been easy. Become a mage and train in Combat, the most prestigious faction of magic. Yet when she arrives, Ry finds herself competing against friend and foe for one of the exalted apprenticeships. Everyone is rooting for her to fail—first and foremost among them is Prince Darren, the school prodigy who has done nothing but make life miserable since she arrived. Will Ry survive, or will her dream go down in flames?
The author originally left this series with three books. It was even worst than Angelfall and Delirium. The last line of the book was literally The End. Thank god the author picked up the series again in 2017, and concluded the series properly, although still with a bittersweet ending.