The very nature of most player characters, and monsters, is to act, to do stuff, which makes the concept of creatures based around sloth particularly interesting. The end result here is one of the better entries in the Monsters of Sin series, which should be taken as high praise.
Once again, the booklet had 6 pages of content, with one page dedicated to a discussion of the sin, and a template for slothful creatures, and half a page to a couple of short cautionary tales set in the Midgard campaign setting. Given the nature of sloth, the template, uniquely for those in the series, lowers the CR of the creature that takes it, making the creature weaker. It's notable then, that one of creatures in the book attacks, in part, by giving its opponents the template!
The creatures themselves range from CR4 to CR17, and are all both original and directly linked to the topic of the book. There's a slothful giant that attacks through its sheer mass rather than more energetic combat, a lazy dragon with an unusual breath weapon, and an outsider that weakens its opponents in an original way.
As is often the case with this series, the last creature is the most interesting (although also the highest level). This vast outsider truly embodies the power of sloth, getting other creatures to act on its behalf, while itself remaining protected by the force of its own inertia. It's really quite a neat idea, and one that works well.
The artwork, as usual, is good, and I didn't spot any proofing errors. Even if you're not particularly interested in the other entries in the series, this one provides some interesting and original opponents, and is recommended.
[5 of 5 Stars!]