The stone god awakens, by Philip Jose Farmer. That’s one hell of a book jacket.
Anyway I can’t say I’m a big Farmer fan. I haven’t really read enough of his work to form a general opinion. In fact this is the first novel of his I’ve read, and I’m not sure if I’ve ready stories by him in anthologies.
The premise of the book is that a physicist is frozen in time for millions year by some largely unexplained experiment, and emerges into a world populated by primitive humanoids that seem both human and animal. He takes up with some cat-people who have been worshiping his frozen form as a god, and introduces bows, horse riding, and gun powder to them, and then gets increasingly involved in the various races and begins a search for other humans as well as battling another ‘god’ — a vast banyan tree system that threatens to consume the entire land mass.
The tree is huge — miles and miles across; thousands and thousands of feet tall; with thousands of branches. Forests, rivers, and lakes form within the branches, and many strange animals and humanoids populate it. It is fairly inspiring as a strange environment to explore: rivers course along some branches, to fall precipitously into waterfalls thousands of feet down; the ground beneath the tree is a perpetually dark, swampy mire, where bits of the tree occasionally crash down, and various vermin inhabit the decaying branches. The tree itself may in fact be intelligent (why spoil the book?)
The other thing I liked about this book was that it provided a fairly a somewhat consistent world for Gamma World type adventures. The world as we knew is long gone, and the flora and fauna are all unrecognizable. It also suggests what is probably the most logical way to run GW: the PCs, like the protagonist, are from the past (or another world) and are discovering the mysterious environment. Other have suggested running mutant PCs in the GW as tokens of species, and this world would at least make mutated animals viable species.
Apart from using the book as inspiration for gaming, though, I would not really recommend it as literature. The hero is never all that interesting, and his main conflict is whether or not he’s attracted to a cat-woman (I’m guessing Farmer is). The book is not broken into chapters but is more like a really long short story, which gets kind of tedious. The bad guys are obviously bad from the get-go, but no one has very clear or realistic motivations. The book also fails to end with any real sense of resolution, and it seems like Farmer may have wanted to leave opening for a sequel. If not, he actually made a fairly bold and original choice, to leave the villain undefeated and hero wondering if it is worth fighting. I guess I should give him the benefit of the doubt and say he breaks conventions a little; still, I had a lot of trouble caring about the characters or even telling most of them apart except by species.

I’ve read a lot of PJF, and a lot of his stuff feels that way: he takes a great idea or three, stirs in a pretty basic conflict, and people duke it out for a while until they just kind of stop and say “NOW what?”
The atomic suspension idea that freezes the title character for a couple millennia also (originally?) showed up in “The Sliced-Crosswise Only-On-Tuesday World” and later the Dayworld books, where society basically conserves resources by keeping 6/7ths of the population in suspended animation on any given day (For the main character of the short story, every day is Tuesday. He falls in love with a girl he never met, because she’s only alive on Wednesday…)
Regardless of the story’s merits: Dat Cover Art!