I'm not hugely familiar with Terry Pratchett and Discworld as other fans are, but my real introduction to the series -- Going Postal -- was a great read with engaging characters and a fascinating look at how stamps came to be. Sure, it was a fictional fantasy story, but it felt like Pratchett did his research to get an accurate look at how folks adopted the system of stamps. Its sequel, Making Money, featured the same characters, but focused on developing a money system and mint, and now Raising Steam is the latest "Industrial Discworld" novel, featuring Moist von Lipwig and the rise of the train empire. Unfortunately, it falls flat, in a number of ways.
Part of what made Going Postal so good was the idea that Moist, our hero, created the idea of using stamps pretty much on his own. In Making Money, Moist steps in to revive a failing industry, so the story is less about how he develops a system and more about how he refines and redefines it. Raising Steam really isn't about Moist at all, since most of the developments -- the steam engine, the rail lines, the infrastructure, and the like -- all take place outside of him. He's just there to smooth things along, and as interesting as Dick Simnel, the straightforward inventor of the steam engine, is, he's not really enough to carry the story. As much as the story jumps around, he can't.
The story does jump around a lot, from one city to the next, from one character to the next, enough so that it's hard to get a handle on exactly where the story is going. Pratchett touches on the major strokes of what rail development was -- the building of the engines, the building of the lines, the stations, the stopovers, and all the major infrastructure that such a thing requires -- so it was similar to the previous books in that respect, but the sprawling nature of developing a rail system is too much for one book. Time flies past in the story, so that instead of seeing the entire story play out over a matter of months, instead we're looking at a span of years. In fact, the story opens with the invention of the steam engine, so we don't even get to see a lot of the trial and error that went into creating the engines themselves. It just happens, and the story begins.
I'm not familiar enough with Pratchett's style to know if this deviation is typical or not, but based on the other two books in this side series, Raising Steam doesn't compare. It feels tedious and plodding, and boring in many places. It's not even as readable as I remember his other books being (there were lots of phrasing and punctuation choices that stopped me cold during parts of the narrative because I couldn't figure out what he was saying), so I can't even recommend it for that reason. Aside from the melting-pot subplot that involves the dwarfs, trolls, and goblins being accepted by society and each other, it's just not very interesting.
Die-hard Pratchett fans will certainly read this (and probably disagree with everything I've written here), but for casual readers of his fiction, I wouldn't recommend this book. Instead, go back and re-read Going Postal. It has the charm and interest level that I expected this book to have.