I bought this book since I thought it might be helpful. However, some solutions are terrible although final answer is correct.
The solution in class (USA) is much simpler and clearer.
This is true for Goldstein's classical mechanics.
Several people from Waseda wrote a book, but the solution is "B-" level (Ka in Japan).
That might be the level of Waseda in world level. If you have a difficulty to solve problem, check internet.
It is easy to find the help. Sakurai is a standard textbook in USA. Many schools post the solution.