The Great A'Tuin moves. On his back, 4 Elephants. (There was a 5th elephant, but it crashed in Uberwald and left fat deposits.) And on the elephants' trunks, a flat surface with hub and rim.
Yep, Terry Pratchett released the 40th installment of Discworld, Raising Steam, in which Moist van Lipwig (Of Going Postal and Making Money fame) gets to help start Discworld's first railroad. Not that he's alone in this, as just about everyone from Ankh-Morpork makes at least a cameo in the course of the narrative. We also get a peek at how politics on the disc have evolved following the events of both Thud! and Snuff, which is to say the truce between the dwarfs and the trolls still holds and goblins are quickly becoming a civilized race. (In fact, it turns out the goblins love technology, and have become adept at running clacks towers as well as helping with the railroad. Also, Adora, Moist's wife, is doing for the goblins what she did for the golems. Looking out for their rights and protecting them from exploitation.)
As Lord Vetinari is involved in the railroad building (essentially making sure Moist is protecting the city's interest in it), politics ensues. Beyond the normal stuff (the railroad connecting with the Sto-Lat plains allows for urban flight to happen to a degree), we also get to deal with the grags (Dwarven fundamentalists) who remain unhappy about how Dwarf culture is evolving. This leads to burning down Clacks towers, sabotaging the railroad as the Uberwald Express comes rushing through, and also usurping the Scone of Stone while the king is in Quirm having parley with the Diamond King of the Trolls.
As this is Discwrld, there's a heck of a lot going on. As usual, Pratchett (and probably his daughter*) does a marvellous job of balancing several different story lines, from the Goblin workforce to the sentient locomotive engine, from Moist selling the railway to Blackboard Monitor Samuel Vimes. (Sadly, the witches don't show up, although Nanny Ogg is mentioned in passing as visiting the Lancre Clacks towers.)
To go too far in depth with the plot would ruin the book for folks. so let's leave it at Although Moist is not among my favorite characters in the Disc, Raising Steam is still an exciting ride that advances Discworld into 19th centure fantasy technology.
*Pratchett has Alzheimer's dementia, sadly. By all accounts, his daughter Rhianna is poised to continue the series when Sir Terry reaches a point where he can't write.