Every generation, a sci-fi novel comes along that revolutionizes the genre, influencing the way we discuss similar stories for years to come. I think it's pretty safe to say that this was not one of those times, despite the cover blurb's presumptive assertion that this is "probably the finest novel of alien invasion ever written."
After all, when was the last time you read an alien-invasion story that featured a race of extraterrestrials in the form of hyper-intelligent, human-sized elephants with two trunks? Never? I thought as much.
Basically, what you see on the tin is what you get. Alien pachyderms from Alpha Centauri attack Earth, prompting humanity to join forces to repel the invaders, and it's treated quite earnestly by the writers, Larry Niven and Jerry Pournelle, big shots in the sci-fi world. But notwithstanding the ridiculousness of that premise, I wouldn't suggest that you throw this book to the ground and trample it beneath your round, meaty hooves.
Though it was received somewhat lukewarm and doesn't have a large fanbase, I will say that this book has an interesting story to tell in its own right. If you're at all intrigued by the image of an evil elephant wielding a blaster gun in one of its prehensile trunks, looking around the corner with a hand mirror in an action-movie-style standoff, you'll probably enjoy this tome. If you want to see a different approach to the alien invasion story in which the enemy doesn't have the typical "pack" mentality that invaders tend to be characterized with, but rather a "herd" mentality (meaning they don't fight merely to eradicate, eat, or enslave their enemies, but to establish dominance and incorporate the remaining losers into the winning herd) then this is your book.
Suggested sequel title if Niven and Pournelle ever get around to it: "Revenge of the Herd: An Elephant Never Forgets".