This morning I realized that the long-book/short-book debate parallels the relationship between Ticknor, laboring for ten years on his article about canals, and his friend Prescott, writing his three-volume histories by dictation, "never trifling with style, but with style flowing from his lips." Poor Ticknor - never on the popular side of any argument!
As you've probably deduced from our discussion, Ticknor is primarily a character study, painted in the hero's own words. Not incidentally, it is also, in part, a biography of Prescott, told by our hero.
Ed's comment on the novel's sources reminds me of the unusual note that occurs at the end of the novel:
Ticknor was inspired by the Life of William Hickling Prescott, by George Ticknor (Philadelphia: J. B. Lippencott Company, 1863). Sentences and scenes have been borrowed from that book, and from the work of Florence Nightengale, Marie Stopes, Havelock Ellis, Sofia Tolstoy, among other writers.
I haven't looked at the sources, but I'd expect we're not exactly talking here about the literary equivalent of the "mash-up." Although I admit, I've had some fun trying to guess where those sentences and scenes are. The platitudinous tributes to Prescott that are sprinkled throughout the book ring so true to the period that I'd be shocked to see that some of them aren't from The Life. Part II of the book, excepting the first paragraph, begins with a straightforward biographical essay on Prescott in which our hero Ticknor moves entirely into the background. If this isn't verbatim, I'd love to see what changes Heti introduces. I don't know anything about the life of Marie Stopes, but Florence Nightingale is clearly the troublesome nurse who should be sent back to Europe.
One of the fascinating things about this book, of course, is that fact that the characters are based on real people. What Heti has supplied is a fictional emotional life behind the factual events.