Book Eight in the Hal Spacejock series
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 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.
Simon Haynes is the author of eight Hal Spacejock novels for teens/adults, three Hal Junior novels for ages 8-99, the Harriet Walsh series for teens/adults, and over a dozen short stories spanning fantasy, thrillers and hard science fiction. If you're looking for super-heroes with overwhelming powers, this is the wrong author for you, because Simon's work typically features the underdog fighting for survival against powerful opponents.
All Simon's novels are self-contained, with a beginning, a middle and a proper ending. They're not sequels, they don't end on a cliffhanger, and you could start or end your journey with any book in the series. (Some events from earlier books are referenced in later ones, so it makes sense to read them in order, but it's not essential.)