In my review for volume 3, I expressed concern about how long the power creep of the titular character would be manageable going forward, given how strong she was getting by the end of that novel. Volume 4 proves definitively that this isn't going to be a problem for a while yet, as while the spider may have more or less mastered the dungeon and gone on the psychic offensive against her mother, the Queen Taratect can't be beaten easily. There are also other powerful foes out there who can (quite literally) tear her apart if she gets careless, but at least she gets a new ability and learns some harsh lessons about overconfidence.

The third novel made it clearer that the spider and Shun were operating in different time frames, nearly 15 years apart, but the fourth novel lays that truth out much more starkly. The progression of Shun's story makes numerous references to the results of the spider's actions being in the past, while in the spider's story the “evil god” watching her spills some interesting clarifications about where he is, why the Demon Lord and Hero's magic caused this effect, and why the reincarnations' classroom got hit in the first place. (Unsurprisingly, it wasn't totally by chance.) This volume also clarifies earlier suggestions that the spider is the being known as the Nightmare of the Labyrinth in Shun's time frame, though the true nature of the Nightmare Vestiges is still a mystery to be untangled. The crowning jewel of info we get is the timeline provided at the end of the book, which lays out exactly when events to this point have happened relevant to each other. While that does take away some of the mystery from the plot's construction, it also makes the overall story much easier to follow. I don't recommend looking at it until after you have finished this novel, however, as it does spoil some events that happen therein.

The last novel had also started to suggest that the spider is going to become the Demon Lord of Shun's time frame. This novel only throws more fuel on that fire, as most signs seem to point toward that conclusion, including the Demon Lord's desire not to kill reincarnates. That said, the story is still allowing itself some wiggle room on that point, especially with the revelation concerning the Demon Lord in the spider's time frame. The implied bitter enemy of the Demon Lord of Shun's time also makes little sense at this point if the spider becomes the Demon Lord.

The spider side of the story is definitely the more dynamic one at this point, even though Shun and his party get into a couple of minor battles. The revelations concerning the other reincarnations aren't ground-shaking but still flesh out the overall picture more, though the affiliation of some leaves the sense that much more story is coming there. The occasional other snippets with implications of what some villains are discussing also adds further spice to the mix. Even if they aren't used much, the multiple perspectives contribute to a fun overall picture, handled skillfully enough not to get in the way.

The breezy stream-of-consciousness writing style still remains one of So I'm a Spider's biggest plusses; I haven't seen many other LN authors handle first-person perspective anywhere near as entertainingly as Okina Baba. Baba's talent for exciting action scenes, where the heroine pulls off many tricks and stunts rather than simply overpowering her foes, also remains as sharp as ever. Characterizations don't get as much emphasis this time around, although the revelation that Fei was pretty vain in her human days has some potential to stir up that pot.

As per the norm for these novels, various monster stat blocks are scattered throughout, a glossy dual-fold illustration page features the spider on one side and certain humanoid characters on the other, and other black-and-white illustrations are interspersed. The 246 pages close with a two-page Afterword written in the same style as the novel's content.

Overall, this is another strong installment in one of the most fun isekai reincarnation stories out there. I eagerly await what the upcoming anime adaptation will do with this material.