To be clear, this book is not meant as a definitive guide to etiquette. Many of the criticisms levelled against it seem to assume that every gentleman's guide should be the same, and boring.
Someone suggested that this work was about "faking" an interest in things such as classical music, nothing can be farther from the truth. If classical music is not a keen interest, should you stand there like a dolt as it is discussed? Of course not! A true gentleman is familiar with all things, and this book seeks to familiarize the unfamiliar. So, if you don't know classical music, or jazz, or photography, or entertaining, etc, etc, read on.
As for the language, this work is very verbose. But that is part of what makes the read so enjoyable, it is not at all dry.
In the positive, this book seeks to create a modern gentleman, not someone straight out of 1854, and in doing so may suggest some unconvential practices. It seems the spirit of this book is to live large, and be live like a gentleman while doing so.