I would maybe give it a 3 and a half starts instead. The first few chapters were very good in that in seemed like the author was going to dive deeper than they did on technical details related to the kernel. For instance, he described some basic concepts that perhaps most people would already be familiar with reading the book, but missed opportunities to describe cgroups and capabilities in detail, as well as covering data that can be obtained abut the host via /proc and /proc/fs. Some chapters felt more like review of tools, which I appreciated at times, but he leaned a bit too much on tooling how-tos in some chapters. I still enjoyed it and was able to make note of several other areas for further investigation.