42 is the Answer to the Ultimate Question of Life but I guess I wouldn’t suggest it as the optimal global temperature.
I didn’t know this but the final and last book of the series was published back in 2009.
http://en.wikipedia.org/wiki/The_Hitchhiker%27s_Guide_to_the_Galaxy
It was announced on 17 September 2008 that the author of Artemis Fowl, Eoin Colfer, had been commissioned to write the sixth instalment entitled And Another Thing... with the support of Jane Belson, Adams’ widow.[20][21]
The story begins as death rays bear down on Earth, and the characters awaken from a virtual reality. Zaphod picks them up shortly before they’re killed, but completely fails to escape the death beams. They are then saved by Bowerick Wowbagger, the Infinitely Prolonged, whom they agree to help kill. Zaphod travels to Asgard to get Thor’s help. In the meantime, the Vogons are heading to destroy a colony of people who also escaped Earth’s destruction, on the planet Nano. Arthur, Wowbagger, Trillian and Random head to Nano to try to stop the Vogons, and on the journey, Wowbagger and Trillian fall in love, making Wowbagger question whether or not he wants to be killed. Zaphod arrives with Thor, who then signs up to be the planet’s God. With Random’s help, Thor almost kills Wowbagger. Wowbagger, who merely loses his immortality, then marries Trillian.
Thor then stops the first Vogon attack, and apparently dies. Meanwhile, Constant Mown, son of Prostetnic Jeltz, convinces his father that the people on the planet are not citizens of Earth, but are, in fact, citizens of Nano, which means that it would be illegal to kill them. As the book draws to a close, Arthur is on his way to check out a possible university for Random, when, during a hyperspace jump, he is flung across alternate universes, has a brief encounter with Fenchurch, and ends up exactly where he’d want to be. And then the Vogons turn up again.