The Dresden Files are great. They’re quick reads (like 300-500 pages iirc), but there are like 17, so it kinda matches your length requirements. It’s about an openly practicing wizard in Chicago, though nobody believes he can do real magic. They’re generally about stopping supernatural monsters or crime. First book: Storm Front, author: Jim Butcher
Also by Jim Butcher: Codex Alera (first book: Furies of Calderon) I’ve only read the first book & a half of this series, but it is very epic. It is set in a setting based off of the Roman Empire.
Powder Mage by Brian McClellan is also good, doesn’t fit your series length requirement though, being a trilogy and a sequel trilogy.
All of the above books have some adult themes (first two more than the third), if that bothers you.