First impression is that they are very small and yes they are. The lenses are small but its the wide which might be a problem. they are 13cm to the outside edge of arms. On a plus they do seem to be well made and I like the box.
I like to have a book in my hands so I can't comment on the Kindle issues with this book. I found the book actually quite good in that it has simple examples which it builds on. As an example it takes you through building a bar chart and then the stages to get it looking nice, sorted, animated and then interactive. It takes time to explain what the issues are and how it solves them. Yes its an introduction but to be honest there isn't much out there on D3 that gets you coding.
I found when I was learning Erlang that this book was beyond beginner level. I have coded SQL for many years and Erlang is a different concept being a functional language. I tried this book first but found after reading the introduction to Erlang by Laurent that I wished I had started there.