The Dastard - I found the villain in this one pretty interesting. He trades his soul to a demon for the power to change history, but he isn't really evil in his use of this power, just a total jerk. During the course of the plot, he travels with a half-dragon girl, and has to battle the Sea Hag (the main villain in the earlier Golem in the Gears), who has escaped from the Brain Coral. The Hag really isn't that significant to the plot, though, and seems to be there primarily so her that Piers can compare her variety of evil to the Dastard's milder deeds. It's a good story, but I think the idea of grown-up versions of the three daughters of Ivy and Grey who are children in ordinary Xanth is overly confusing and convenient at the same time. See, there's a separate world where everyone who has the potential to exist in Xanth lives, and after introducing this place in Faun & Games, Piers seemed to have the need to use it in every subsequent book.
Swell Foop - In order to rescue the captive Demon Earth, a motley assortment of characters has to track down the magic rings that will enable them to find the Swell Foop, an artifact that can control Demons. Not one of the more memorable books in the series, but an enjoyable read nonetheless.
Up in a Heaval - Like Roc and a Hard Place, this one visits a lot of the characters and locations from the earlier books, this time by making a Demonic construct deliver letters all over the country. It also gives Jenny Elf's cat Sammy a role apart from Jenny herself.
Cube Route - By this time (and this is the twenty-seventh book in the series), it seems like Piers was somewhat bored of Xanth itself, and had to introduce new worlds. Not only is there another visit to the moons of Ida, but the book also introduces Counter Xanth, and there's a crossover with one of Anthony's other series. I haven't read any of the Apprentice Adept books, but the brief visit to Phaze in this story is fairly short and uneventful, making it seem like more of an advertisement than a real plot point.
Currant Events - I think this book was more successful than some of the other later ones, at least partially because it focuses on aspects of Xanth that he'd already established but never really explored, rather than concentrating on new lands. Piers had mentioned a few times that the nine Muses from Greek mythology make their home in Xanth, and that Clio, the Muse of History, is the real writer of the books. Here, we finally see Clio as a main character. Since this IS a Piers Anthony book, part of it involves her hooking up with another character, but the relationship between somewhat older Xanthians is a nice change from all the young lovers we've been seeing. There's also an odd mixture of mythologies, in that not only do the Muses appear, but so do Paul Bunyan and Morgan le Fay.
The local library doesn't have the next book, Pet Peeve, and I'll probably wait until after the holidays to locate a copy. After that, I think there are only three more Xanth novels currently out on the market. In the meantime, I've found a few other things to read.