I found this book excruciating to read. The grammar is poor, as is the style and the book reads more a collection of related statements than a well-thought-out treatise on a topic.
There is some useful information in here on personality types and their relevance to e-Learning, if you can bear to read that far. However, it is very much 'personality types', this isn't a general book on learning styles research. Hills glosses over Kolb and Honey-Mumford learning styles research to focus on Myers-Briggs personality types and apply them to e-Learning.
If you're designing e-Learning systems then Honey-Mumford or Kolb are actually simpler to use than Myers-Briggs. If you're reseraching impact of cognitive style on e-learning you'd be better off reading Kolb