Since this is one of my favorite movies ever I had to buy the novel when I saw it in a used bookstore, I recall it being quite good. It is written by the respected French author Pierre Boule, but the story is somewhat different from the film.
My friend picked this one up for me at a thrift store recently and I can only hope that the book is better than the movie, which was the worst in the series. If I'm not mistaken the cover image is actually from Conquest of the Planet of the Apes, and not Battle. In a search for novelisations of the other films I found one site that has 'em all, Hunter's Planet of the Apes Archive, enjoy.