The book is divided into three parts: the first part talks about what 'the cloud' is and how SharePoint fits into it (basically, SharePoint Online as part of Office 365), and provides some information about its capabilities. Phil also dedicates a chapter to planning for SharePoint Online, including the Information Architecture, security, customisations, and training. In my opinion, extremely important in every SharePoint related activity.
The second part of the book, titled Deploying SharePoint in the Public Cloud, goes a bit more into detail how to start using and managing SharePoint Online. The most interesting chapter here is Chapter 6: Migrating to SharePoint Online, in which Phil lists several approaches of how you can move your content from its existing location (with a major focus on on-premise SharePoint) to SharePoint Online.
Lastly, the third part of the book talks about SharePoint in the Private Cloud. How can you set up SharePoint in your company inside your own Private Cloud, including all the relevant automation. Topics here include virtualisation with Hyper-V, a very good discussion about multitenancy in SharePoint, and how to configure tenant-aware service applications and site applications. While I initially thought that this part of the book is the least interesting to me, it gave me a much better idea of how Microsoft has (possibly) set up and configured Office 365, and why some functionality is not available at the moment (e.g. FAST Search).
What I missed a bit in the book was a better analysis of when and why it makes sense to use cloud technology. While there is a section in the first part of the book that covers this topic, I felt that it was a bit too short, and more information could have been provided. Another thing that confused me occasionally in the first and second part of the book was that there was not always a clear differentiation between SharePoint Online Standard (which you get as part of the 'regular' Office 365) and SharePoint Online Dedicated (which you have to contact MS for). While most of the time Phil notes what is available in or applicable to each of these two and what isn't, I found myself thinking sometimes "this isn't possible in Office 365", only to realise that Phil was referring to the Dedicated version.
Overall, however, I would say that it's a quite good book for anyone interested in learning more about cloud-based SharePoint, providing very useful information for any medium or large sized organisation.