It's really hard post-hoc reviewing books that begin long-running series you've already read. It's too easy to overlook things that gave pause on first read, or were unclear, because you know where it's going. On the other hand, it's sometimes hard to see the really clever flourishes in the world-building, the exact things that pulled you in the first time, because this world and it's inhabitants are already old friends.
In any case, the Hollows books are rip-roaring urban fantasy with a pretty great female protagonist. There's romance, but these are not PNR (although there's the odd sexytimes scene, maybe 4-5 times in the entire first ten books, unless I'm misremembering). I mention this because I'm so over reading poorly written "PNR" that's just an excuse for horribad erotica, and I know I'm not alone there.
As mentioned, long but completed series, I'm just gonna suggest you pick up the first book and see if you like it.
But if you're interested in more thoughts, read on. Consider yourselves warned, this might get long. Even for one of my reviews.