Mohammed and Aravind have done a good job at covering a broad range of topics related to ESXi. I was pleased to see basic topics such as automated installs and securing your hosts alongside advanced topics like DRS and HA.
I skimmed through most of the book, but spent some more time on the final chapter re vSphere Update Manager, because that was an outstanding task I had to complete on my own platforms. There are detailed and comprehensive instructions to guide the reader through the process of setting up and using Update Manager.
Unfortunately, due to the rapidly changing nature of the content, the book is already out of date. It’s written with ESXi 5.1 in mind, and ESXi 5.5 was released in Sept 2013. Fortunately vSphere Web Client was used for all the screenshots (with the exception of Update Manager, but that would still the case on ESXi 5.5), so most of the book should translate well to ESXi 5.5. Certain portions of book won’t line up with the latest version of ESXi, especially chapter #2, regarding the installation of vCenter Server. (SSO was rewritten for ESXi 5.5, for example)
Overall, I’d rate it as a good read for someone wanting to gain familiarity with the ESXi platform, and as a good reference for those who use it routinely, but may not have explored it’s entire featureset.