Because Sprigge has an academic reputation as a serious philosophical commentator on certain issues in British Idealism and Santayana studies, I suppose I expected a serious, high level treatment of the problem of existence.
Instead, what Sprigge has written is a very superficial freshman-college level introduction to the philosophical problem of existence, organized by philosopher or school of thought. This is all fine - such a book has its place. It just isn't what I was expecting.
Add to that that the book is a bit unfashionable and dated at any rate (written at a time when the obligatory nod to continental philosophy involved a recognition of Sartre).
It is a fine book as written, as long as you know what you are buying.