It is a remarkable fact that one of the best-known novels by one of the greatest 19th-century English novelists has never been published in the form its author intended. Anthony Trollope wrote The Duke’s Children as a four-volume work but then reduced it to three, necessitating the loss of almost a quarter of his original text. The precise reason is lost to posterity but is likely to have been a demand from his publishers on the grounds of economy; it would not have come from Trollope himself, who had earlier written in his Autobiography: ‘I am at a loss to know how such a task could be performed. I could burn the MS., no doubt, and write another book on the same story; but how two words out of every six are to be withdrawn from a written novel, I cannot conceive.’That's over a quarter of the book missing. But here's another fact: It's also a hair beneath the recommended low end of length for a modern novel, with 115 as the high end and 90,000 as "the sweet spot."
Yet this is precisely what he was obliged to do, and 65,000 words ended up on the cutting-room floor. As he wrote to John Blackwood not long after making the revisions: ‘I am bound to say that I have never found myself able to effect changes in the plot of a story. Small as the links are, one little thing hangs on another to such an extent that any change sets the whole narrative wrong. There are so many inﬁnitesimal allusions to what is past, that the whole should be rewritten or it will be faulty.’ It was meticulous, exacting and soul-destroying work.
Now, Phineas at Bay clocks in at 171,461 (including the Postscript and Table of Contents, so a bit less, really). That's still well under either of the two Phineas novels by Trollope.
The factor that tipped me in favor of self-publishing was just that--a length such as that recommended by agents would not have allowed for a Trollopian feel. You need details for that, what the Folio Society calls "the massive accumulation of details." There has to be a feeling of capaciousness, of breadth. Self-publishing meant I could avoid the dilemma that Trollope himself had to face.