I should preface my review with my strongly held view that many pet owners coddle, indulge, spoil, anthropomorphize and ruin their pets (frequently as a substitute for human interaction). This novel is about such a pet owner, who discovers his Dachshund Lily is suffering from cancer. He refers to the cancer as an "octopus" due to the shape of the tumor (hence the title) and also anthropomorphizes the tumor. What follows is an account of the owner's fight against the tumor (Lily takes it mostly in stride) -- some of it semi-realistic and some of it an odd, gratuitous, and dreamlike account of a battle at sea among the three main characters (Lily, the narrator, and the octopus), which felt largely like filler material to make this story novel length (it originally started as a short story, according to an article about the author that prompted me to buy it).
Make no mistake: the book has a lot of passion and some humor. The narrator, a gay man who has broken up with his partner; has Mommy issues, a bad therapist, and a dwindling career; and plays monopoly on Friday nights with Lily is occasionally funny in his angst in a hapless sort of way. Lily is excitable and occasionally amusing. But there wasn't a lot of narrative drive here and a great deal of feeling sorry for oneself. Moreover, it felt like a long session listening to an indulgent pet owner drone on about his four-legged friend.
Perhaps it would be more of a hit with those who are indulgent pet owners. For someone seeking drama and human relationships, this will be no substitute.