Blonde Bombshell, By Tom Holt

Mark Twain was a smart bomb, sent to earth by dogs...

A distant planet, on which dogs are the dominant species and humans are their pets, sends an intelligent bomb to destroy Earth, where we are annoying them by playing our music too loud.

The bomb decides to investigate Earth's defences before blowing it up, and transforms into a humanoid, self-christened Mark Twain. On Earth, he meets Lucy Pavlov, a computer genius and the richest and most beautiful woman on the planet. Throw in an alcoholic banker, a unicorn, some comedy villains and a bunch of dead octopi and you have the ingredients for a comic SF caper reminiscent of Terry Pratchett. Or Douglas Adams, but not quite as good. A fun, undemanding read which will put you in touch with your inner adolescent.