This is a great book for all those who really want to understand the intricacies of the theory of relativity in depth, understand its origin and appreciate the beauty of it.
The language is simple and mathematical formulas are avoided, but that does not diminish the amount of information or analysis of the subject, nor does it makes this book a peace of cake. You may even have to read some of the parts twice to fully grasp them. But the understanding of relativity that the book provides is worth the effort.
This is great product within a reasonable budget for those who want to try their hands at calligraphy. The build quality of the product is very good. You are provided with two tips of different width for versatility in your calligraphy. And the most convenient feature is that you don't need to buy cartridges separately. Any ink will do but I would suggest the use of a good quality ink and paper even if you are an ameture.