This is the third and final book of The Magicians series by Lev Grossman. It has been many years since I read the first two so I didn't remember all the details, just the general gist of things. Still, picking this up after so long was easy enough to do and I don't think I lost much by not remember some of the events of the prior books. I had also recently watched the first season on TV, which I think spans beyond just the first book and helped me remember some of the finer points I had forgotten about.
For my full review, see below. I aim to avoid spoilers for this book, but the other two books may be unavoidable. My readings of the prior books predate my blog, but you can find a brief review of the second book, The Magician King, on Goodreads.