Note: This review will contain spoilers regarding the previous Overlord light novels.
Overlord Vol. 7 is great overall, but a little bit of a mixed bag. After three books that (mostly) put Ainz in a more secondary role, we finally get to focus on him again. In some ways, Invaders of the Great Tomb is still weaning off the format seen in volumes 4-6. In other ways, the layout is closer to volumes 1-3. This book is more of a developmental step forward than its own thing. Multiple events here are certainly going to be important later, even if they seem like little cliff notes now.
Of all the previous books, Vol. 7 most resembles Vol. 4. Like with the Lizardman story, we see Ainz and his group in an almost purely antagonistic role. These other characters are built up and most of them are good, honest folks just living their lives. Despite that, you know that these people are doomed. Not for personal or even particularly malicious reasons. They are pieces in the game Ainz is playing; not so much people as they are mere tools. Maruyama has no problem channeling his inner George R.R. Martin with his characters, often in brutally gruesome fashions.
On the flipside of that, we do get a good portion of the book from Ainz’s point of view. There is more of him as the adventurer Momon, now establishing the persona outside the Kingdom’s borders. Readers also get to see more of Ainz as the ruler of Nazarick, as well as everything that role entails. Going from being a normal Japanese salaryman to the supreme ruler of an evil army is a bit daunting. Seeing Ainz attempting to run an empire a bit like a business while balancing how his minions view him is awkward but humorous.
The majority of the key events for Invaders of the Great Tomb happen towards the end of the story. To put it shortly, this is all a test. Nazarick is still experimenting with how the New World works in comparison to YGGDRASIL. Maybe this will be important in future books; at some point they are likely going to make enemies so maybe they will be invaded and need to know about how their defenses operate differently now. The “test” also sets up some political machinations that will obviously be important within the next book or two…