no. 8, Hal Spacejock
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Hal Spacejock lands on planet Alteia, where he's so distracted by his own problems that he forgets to collect Clunk from the luggage rack. Not to worry, because a couple of old friends free Clunk from the spaceport ... only to reveal a great big ulterior motive: they want him to join their gang ... er, group.
Meanwhile, Hal's remembered his trusty co-pilot at last ... but only because everyone's trying to kill him, and Clunk is big and metal and bulletproof-ish.
Set in the distant future, where humanity spans the galaxy and robots are second-class citizens, Double Trouble is the eighth novel in the Hal Spacejock series. Book nine, Max Damage, is currently in progress.