Kennard's cookbook is an excellent resource for novices and experts alike. The book covers some very common issues with Joomla 1.5 sites that have implications for Search Engine Optimization (SEO). These include how to set document titles, and add meta-data, for example (Chapter 7). For novices, however, it would be helpful to not only explain how to perform these activities, but why one should be concerned with them in the first place. On the topic of SEO, for example, most search engines are much more concerned with descriptive document titles than with accurate meta-data.
For experts, this book goes beyond the typical cookbook of solutions, but in organizing them around larger, significant issues. For example, he covers solutions associated with multilingual sites (Chapter 5) and in writing plugins that are extensible and modular (Chapter 9) to ensure portability and re-use.
Kennard also explains how how to set up a formalized [...] project (Chapter 1), While this is excellent information, I would recommend moving this information to the end of the book, perhaps even as an appendix.
Even if you're working on one of your first Joomla sites or projects, this book will pay for itself. In particular, novices should pay attention to chapters 6, 7, 8, 9, 11 and 12. Because Chapter 11 discusses error handling, I would recommend that new developers start there. Oftentimes frustration with a project arises not from having to troubleshoot, but by not providing yourself with the necessary error handling and reporting to really understand what is happening. This is excellent material.
Overall, the benefits of this book far outweigh what I would consider minor revisions for a second edition. Although I would like to see this book be a little more novice-friendly (add definitions, explanations of relevance, perhaps a glossary), I would still recommend it to both novices and experts alike.