Assuming that you are speaking about Sanderson's Mistborn series, I can say that these are dystopian fantasy novels whose characters use occult powers in their various adventures. The following description of these powers was found on the SciFiCatholic website:
"The Allomantic magic system is inventive and clever. Powers include the ability to manipulate others' emotions, the ability to strengthen the body and heighten the senses, and the ability to push and pull metal objects with the mind, among others."
A strange form of religion is also prevalent in the book. SciFi Catholic describes it this way:
"Though it's never fleshed out in great detail, religion plays a role in the novel. The Lord Ruler has declared himself the 'Sliver of Infinity,' a fragment of God, and forbids worship of any deity besides himself. All other religions have been suppressed and apparently wiped out. Most of the characters swear by the Lord Ruler . . . The Lord Ruler's self-aggrandizement makes him reminiscent of the fictionalized Nebuchadnezzar depicted in the biblical book of Judith, who conquers most of the world and declares 'that all nations should worship Nebuchadnezzar alone, and that all their dialects and tribes should call upon him as a god' (3.8, NRSV)."
In spite of its occult content, SciFi Catholic gave the series a thumbs up, but the review is detailed and gives a good idea of the content.
I have also read intimations by some readers of the series that Sanderson's Mormon faith may be influencing the story in some ways. You can read more about Sanderson's background here.
At present, dystopian fiction such as The Hunger Games and The Maze Runner seems to be the rage among youth and young adults, much of it very well written.
For additional clarity, you might want to visit the website of Michael D. O'Brien who is an expert on the subject of fantasy literature from a Catholic perspective. This blog will give you some idea about his insights into this genre which I hope will help you to discern what kind of fantasy literature is appropriate, what is not, and why.
To conclude: I offer this quote from St. John Bosco which appears on the Catholic Sense Media website because it gives simple and sound advice to any discerning reader:
"Never read books you aren’t sure about…even supposing that these bad books are very well written from a literary point of view. Let me ask you this: Would you drink something you knew was poisoned just because it was offered to you in a golden cup?"