It is truly interesting to consider that this was written 40 years ago. Many of the issues that were foretold in it are actually happening right now. When I read it in high school, I'm not sure I fully "got" many of the references. However, I do clearly remember really liking the book.
Now, moving on to the next two...
Actually, after reading this and "Macroscope", I'm sorry to admit that the "Xanth" series has somewhat soured me on this author. But perhaps I should go back and unearth any non-"Xanth" works of his. Because when he is not churning out the pulpy stuff, he is really quite good.
IMHO of course.
Omnivore, published in 1968, was the first volume in Piers Anthony's Of Man and Manta trilogy. I delved into this series as a teenager in the 1970s, along with his Battle Circle trilogy. At that time, he was commencing the publication of the Xanth series, which appears to have been a dominant part of his output over the years. However, I was disappointed by the first Xanth books and didn't read more by him. Now, I've chosen to reread at least Omnivore, the Piers Anthony book I enjoyed the most, to see how it has endured over the years. My 1977 Corgi edition of the book features stunning wrap-around cover art by Peter Andrew Jones, which makes it perhaps the best among the many editions of Omnivore.
I nearly abandoned the book within the first few pages. The opening scene, depicting loggers engaged in some sort of ritual mass fisticuffs and beer-drinking, was rather cringeworthy. Fortunately, I persisted, as the ideas in the book are truly interesting.
The planet Nacre is dominated by the fungi, life's Third Kingdom. Among them, three types have evolved motility. The slime molds on our own planet move slowly, so the idea isn't too far-fetched. The Nacre mantas, in particular, have achieved fast and flexible movement by highly efficiently utilizing a single foot and being able to change their body shape to almost fly over the terrain. These mantas are sentient carnivores, armed with a sharp tail as a weapon. Of the other two motile species, the fungoid omnivores prey on the fungoid herbivores. The mantas "farm" the herbivores and in turn prey on the omnivores. The herbivores, so to speak, are used by the mantas as bait to catch omnivores.
Humans, of course, are omnivores and struggle to earn the respect of the carnivorous mantas as a result. However, regarding the main three human protagonists, one is a vegetarian, one eats both meat and vegetables, and one needs to drink blood to survive. These three humans thus parallel the motile fungoid lifeforms of Nacre. It's a clever concept. Somehow, the relationships between the humans mirror the relationships between the herbivores, omnivores, and carnivores of Nacre.
Anthony's comparison between the three kingdoms of life on Earth is also thought-provoking. Plants are creative in that they convert sunlight and minerals into life, and plant life seems to arise from nothing. The fungi and bacteria are essential for breaking down dead lifeforms into their constituent minerals; otherwise, there would be no cycle of life and a biosphere couldn't exist. The animals, who eat plants, fungi, and other animals, corresponding to "omnivores" in the tripartite scheme, are not essential for a cyclical biosphere, which only requires creators and destroyers. Further parallels exist between the three kingdoms of life on Earth, the three motile types of fungus on Nacre, and the main three human protagonists. The mantas, it turns out, pose a massive threat to all life on Earth.
Omnivore is excellent science fiction due to its ideas, which seem much more recent than the 1960s. I can't think of any other science fiction book from then or since that features intelligent fungi. However, Anthony's writing isn't uniformly good in Omnivore. As I already mentioned, the opening scene is very strange, and there are jarring moments here and there throughout the book. Nevertheless, perhaps I'll read the other two books in the trilogy, Orn and 0X, just to learn more about these fascinating mantas.
It is quite curious to hear a layman talking about biological evolution, using concepts that he surely learned from popular science books that were probably not very new when he read them. So we have an alternative evolution story told in 1968, on a planet where the "third kingdom" predominates. The characters are empty, and the action doesn't really exist. A whole bunch of flashback jumps really muddles up the story. These days, it would be very cliché, with contact between very different species, followed by a brutal destruction of contaminating aliens on Earth. The concept of the mantas as intelligent super-fungi is quite interesting. Piers Anthony surely has more to offer than the silliness of Xanth.