This is one of my favorite books ever! The Magicians is often called a grown up Harry Potter, and that's partially true - it is literally a mash-up of Harry Potter and the Chronicles of Narnia. However, the characters in The Magicians are not the heroes of those other series - they're more like real high school and college students you might now, with all of a real person's flaws and foibles.
That, in essence, is my favorite thing about this series. The characters in this series sometimes choose to do the right thing, and sometimes they choose the wrong thing, but they always face real-world consequences for their actions. This makes the characters more complicated and nuanced than many/most other fantasy series. It also makes the novels more character-driven rather than plot-driven.
Although the world in this series is a mash-up of Harry Potter and Narnia, the author has put his own unique spin on it. I find the setting to be amazingly detailed - and most importantly, full of magic.