Notes
Destination: Saturn, a standalone novel by Donald A Wollheim (writing as David Grinnell) and Lin Carter.

This volume is a "dos-à-dos" omnibus in the Ace Double series. It also includes Invader on My Back by Philip E. High.

Publisher's Blurb – Lower Cover
In his own way, Ajax Calkins was a modest man. Modestly wealthy – he was just a multi-billionaire. Modestly ambitious – he only wanted a world of his own. Modestly cooperative – he'd let the rest of the universe alone if they would let him alone.

And he did have a world of his own, too. The strange planetoid Ajaxia with its load of pre-asteroidal science was all his – and even Earth recognised that, provided they could come to an agreement.

But it was the sneaky Saturnians that were upsetting his applecart. Rather than make a deal, they fabricated their own Ajax Calkins, set him up, and walked off with Ajaxia.

That was the sort of thing sure to make Ajax lose his modesty – and set off after his kidnapped world single-handed – with the rest of the Earth-Mars fleet too many million miles in the rear!