This book reads like what, essentially, it is. A series of undergraduate lectures from the 50's -- offered by an Ivy-League, tweed-suited, OSS/CIA connected, pompously bourgeoise, 'slightly' radical and donnish (the 'gentleman rebel') Hughes. It is not hagiographic, but he is somewhat sympathetic to Spengler on account of his own apparent hostility towards positivism in historiography and his own tendency towards big-picture simplifications. The best parts of this book, in fact, are those in which he presents (Ch. 2) a clear, thumbnail sketch of the historical temper of the late 19th-early 20th century's political, Romantik modernisms of Nietzsche, Pareto, Sorel, and Bergson -- while reading this I thought it would be an excellent text for some of my less sophisticated students; and his account of World-cycle history in, especially Vico and Danilevsky (the latter being an influence on Putin). His account of Spengler's own system (Ch. 5) can hardly rise above the profound mediocrity of its subject (Spengler's Decline of the West) which, when stripped of its portentious mania -- which so appeals to the undergraduate mind of deracinated bourgeois intellectuals, leaves little residue -- though, admittedly, he view of the 'future' DOES (intuitively grasped) have more than a little resemblence to our present (p. 84f.): the coming Caesarism, the levelling mass-societies of "barrack-cities", and the rise of a new primitivism (think American Mega-Churches).
Usually three-stars means (for me) that the book is junk. But this is a three-star book that many will find it worth reading -- . It's very short, and the last half (Spengler's politics of the '20s and '30s, and his successors and positivist critics) can be safely and quickly skimmed.
The references to two critical articles by R.G. Collingwood are given on p. 96n.14, and there is a very short, but useful account of the Neo-idealism of Croce (to which Collingwood ascribed) at 35f. There is also a good quick review of the 'humanistic Hegelianism' of Jacob Burckhardt at 17ff.