This is a review of the book, not the movie.
In regards to the "love-it vs. hate-it," "Scientology vs. critics" reviews of Battlefield Earth seen here, I should state that I have been an outspoken critic of Scientology for the past several years. Nevertheless, I will still say that Battlefield Earth is an entertaining book – it's far from the "greatest science fiction saga ever written," and it really bogs down in the middle, but it's an enjoyable read nonetheless. In fact, it was the first of L. Ron Hubbard's books that I ever read: I picked it up and read it for the sheer challenge of finishing a thousand-page paperback book. Much of the book is juvenile and laughably silly (such as the evil Brown Limper Staffor and his obsessive hatred for the superhero Johnnie Goodboy Tyler), and some of Hubbard's "science" is so implausible as to be laughable. In one section of the book, the good guys teleport a satellite to a point one light-year away from the planet Psychlo, and they use video enhancement technology to enlarge the image at "six trillion power" magnification to get a view of the planet. Then there's the idea that by placing five nuclear bombs next to each other, they will all go off, one after the other. I'll leave it to better writers than I to point out the obvious flaws to these…but despite their being crucial to the plot, they don't detract from the fact that I enjoyed the book. About half of it is full of rollicking action and intrigue (dampened somewhat by ludicrous stereotypical "good guys" and "bad guys"). Hubbard's Scientology ideas are there within the book, but they're deeply hidden. You'd have to know about Hubbard's obsessive hatred of psychiatry and the way Scientologists refer to psychiatrists and psychologists as "psychs" to understand why he chose "Psychlos" as the name for the evil alien overlords of the whole universe; likewise, the Scientology belief that "man is basically good" is what ensures that the final victory of the book will not leave humanity open to corruption on its own, after the story has ended.
The writing varies from a furious, energetic pace (when the battles and double-dealings are taking place) to tediously slow (when Hubbard plays the material for more additional sub-plots), and as has already been said, the overall tone of the book is that of a junvenile pulp fiction novel. To compare this silliness with grand space opera like E.E. "Doc" Smith's Lensman books would be sacrilege, but Battlefield Earth does stand on its own as an entertaining story. I had trouble getting started with it, and it did bog down, but the final third of the book is fast reading to the very end. This book inspired me to go out and learn more about L. Ron Hubbard and his works…but if you do want to read more, be warned that most of Hubbard's writings are far sillier than what you'll see in "Battlefield Earth." After this book, I worked my way through his ten-book Mission Earth series…which are nothing but a blatant commercial for Scientology, and which are so unbelievably awful that you may want to read them just to see if they live up to their reputation as one of the worst pieces of "science fiction" drivel ever published. Battlefield Earth is an entertaining, fun read…but after this, you may want to read Hubbard's other good book, "Fear." And then you can visit the Introduction to Scientology Web site and learn about his most famous science fiction creation: the "church" of Scientology.