First of all, I'm a HUGE fan of Stroud's Lockwood & Co. books. I've read them a few times. I am on Episode 6 of the Netflix series right now, and I feel like Netflix got this mostly right, surprisingly. However, I do think if you haven't read the books, you might have trouble getting into this story or following it.
I wish they spent more time establishing what the "problem" is and about the big agencies since it's kind of important later on. Also I feel like this is too "edgy". I get it... they are going for a certain teen audience. However, the books were relatively clean. I feel like there has been quite a bit more swearing and drinking, etc. Not really necessary in my opinion.
And while I appreciate Lucy's character being tough here, I feel like her book character was a bit more shy and vulnerable. But maybe I just read it that way.
Also, I felt like the ghost skull in the jar was a bit more fun in the books. Reminded me of Stroud's Bartimaeus... creepy, definitely wants to kill you, but also hilarious. The Netflix version seems mostly just creepy.
Overall, this is one of the truer book adaptations I've seen in a long time. It's spooky (haha) how the scenes (Lockwood's house & other locations) match almost exactly how I saw them in my head. I'm guessing that's due to Stroud's excellent descriptive story telling.
If you haven't yet, READ THE BOOKS. They are a delightful blend of fun, camaraderie and creepy. And kudos to Netflix for mostly capturing that.