The depth of the world is infinite and explored throughout all three books, but the depth of characters is shallower than a puddle in my driveway.
Characters are given basic stories and once they achieve their goals are thrown to the side, happy to exist in their current state and add nothing more to the story. The love interest is never really described and flits in and out with no bearing on the story, the old mentor puts in the bare minimum of effort, the love interests father/owner of the company cares about nothing at all be it right or wrong, the best friend is a caricature of himself, and the bad guy is as scary as a second grade bully and their skill only lasts long enough to put a guise of intimidation before turning into a bumbling boob of failure. The growth of the main character is non existent and luck into everything, while the timeline seems to contradict itself at every gap.
Some plot points are egregiously obvious, while others foreshadow elements to the story that would have been more interesting than the actual story. Certain elements in the worlds are also easily looked up on a web search, but that seemed to be too much effort to bring in, so they were just glossed over like a wrong trivia answer.
I did learn a lot from this book, but it was entirely on what failed and how to infuriate a reader.