This is, simply, a wonderful book. I am not sure how someone really informed about 19th century art would rate this, but for me it was a perfect fit. I found the earlier sections the best - especially on David, Pirenesi, Ingres, Goya, Turner, Gericault, Delacroix.
I also cannot say that I now know what Romantic means - in fact, Clark's thesis is that in every 'romantic', there resides a classicst - and vice versa.
But none of that matters for the ranking of this excellent book.