|I still say he looks like Luigi.|
Adventure Constant. This one uses travel to parallel dimensions rather than space, postulating a world where the physical laws of the universe encourage swashbuckling and derring-do. I suspect Jon especially enjoyed the world-building on this one, what with the Panama Canal becoming a lizardman-infested suicide run, Hawaii still an independent kingdom, and the US equivalent run by an office called the Autocrat of Liberty, the current holder of which is described as a "bombastic business tycoon who had rallied the common man to his cause and was even now attempting to roust the cancerous elitists and their foot soldiers from the country." OK, that last one probably didn't take much imagination.
As a crossover enthusiast, I also need to mention the couple of times that Jack Dashing, the hero from our world transported via crashing rocket to this new one, makes a literary reference only to discover that he's accidentally talking about real people. When this happens to the Three Musketeers it's kind of understandable, since half the characters in that work were real people anyway, but when Jack mouths off to a British spy about his 00 number, he barely manages to get the words "secret agent named James -" out before the spy is question goes from demanding where he heard that to ranting about fraudulent poster boys.
Space Princess. In this case, however, the princess is an infant, rescued by a fairly standard American Catholic family and caught up in the political intrigue and space combat that naturally follows. Jon does a neat trick here by making a setting that shares some broad similarities with that of Sudden Rescue - both are interstellar monarchies - but is quite individual at the same time. In fact it reminds me a bit of a lighter and softer Warhammer 40,000, what with all the cathedral- and chapel-shaped ships being used by the Space Catholics (the red crescent fighters and minaret-bedecked capital ships of the Holy Terra-threatening enemy weren't terribly subtle, either). But the best part is the way in which the ordinary family rises to their very un-ordinary circumstances.
In a way, (and given a flexible definition of "ordinary") that's something that all three of these works have in common. In addition, of course, to being fun, adventure-filled works that rest on sound Christian principles without being preachy. The heroes are all heroic, in every sense of the world, and their sense of optimism makes a fine alternative to the too often nihilistic spirit present in many SF works today.