This is the concluding volume to Neal Stephenson's "Baroque Cycle", which has occupied my reading time for longer than I'd like to admit. (In my defense, I took a couple of breaks to read lighter fare.)
The final volume follows (mainly) the adventures of Daniel Waterhouse as he finally arrives in 1714 England after a perilous voyage from Massachusetts. He's made this journey at the behest of Princess Caroline, who wants the dispute between Newton and Leibniz settled in order to put the beginnings of modernity on a firmer philosophical foundation.
That didn't work out, as is obvious when viewed from our vantage. But the fun is in the journey. In addition to Daniel, fictional friends from the previous books appear, most notably Eliza and Jack Shaftoe. Will they ever get back together? They rub shoulders with actual historical figures: Newton and Leibniz, of course, but we also get Peter the Great, Handel, Louis XIV, Christopher Wren, and many others.
It's obvious that Stephenson had access to a time machine, which he used to tour early-eighteenth-century London; it's described in vivid and meticulous detail.
Reading the whole thing works out to be about 2600 pages of unlarge type and unwide margins, so it's not a task to be undertaken lightly. But 'twas well worth it to see the Phant'sy well-concluded. For me, Stephenson is an automatic buy-in-hardback to the end of his life, or mine.