Not much to say really. Classic Dr Who, Romana, K9 and a worthy villain, in equally classic Adams style. Gareth Roberts did a great job, it's not easy to see the seams, and with someone as distinctive as Adams that is quite a compliment.
As daughter who gave it to me for my b'day said "I saw this and had a nerdgasm".
Definitely reminiscent of Dirk Gently, which is actually my favourite Adams book, but shades of H2G2 as well (and a homage in the second to last chapter that truly made me smile.)
Very close to a 5, only not getting one because it's not quite up to Dirk or H2G2. But it's darn close.