Three stars at best. The mathematics is correct, and let's leave it at that.
This is not a textbook. This is a monograph. The title of this book is misleading. It is not a book on Mathematical Physics. This is a book on special functions and equations, such as: Bessel, Hankel, Lagrange, Leguerre, Laplace, Poisson, Euler, Gamma, Storm-Liouville, and more. And yes, these functions and equations are used in physics. But so is group theory. Being a mathematics book, the notation is very important. Originally written back in 1937, it somewhat uses the notation of the time. The laplacian is written as a simple delta. This is confusing at times because then he also uses delta = (x1 - x0). He interchangeably uses index notation, $a_n$ and differential notation $y_x$.
If you want an old fashion book on special functions, you might want to check this out. It is very wide and very shallow. I doubt you will get much out of it, but it might fill in a special twist you could be interested in.
I expected more and got less.
I will, in the future, read Volume 2, as part of a personal goal. I hope it will be better, but I doubt it.
A little side note: This is the third book this spring that I have read that have misleading titles; writing to learn - with no learning, proofs as a story - with no story, and mathematical physics - with no physics.