He is obviously very well-educated in earth literature and history and also displays considerable cunning and capacity for bullying armed aliens into doing his bidding. A formidable individual in a tight spot (his battle cries have included "God send the Right!", "Kristmenn, Krossmenn, Kongsmenn!", and "Heineken Bier!") he prefers indulging in material luxuries to personal heroism, which is why he has employees. He routinely describes himself as an old, weak, sinful man, but this appears to be false modesty, since he usually follows it by lamenting that his subordinates (or humanity in general) would be unable to accomplish anything without his input. Indeed, this is usually borne out, for van Rijn's great intellect usually proves crucial to solving crises and mysteries that stymie all other characters. In this regard, he is similar to the character of Mycroft Holmes.
Van Rijn is president of the Solar Spice and Liquors Company - an obvious reference to the spice trade with the East Indies which was a prominent feature of the Netherlands' Golden Age in the Seventeenth Century. Clearly, the character is meant to suggest a kind of throwback to the Dutch merchant adventurers of that time, and is far closer to them than to the more civilised and sedate Twentieth Century Dutch. He is capitalist and libertarian in his philosophy, expressing contempt for government and believing that unfettered free commerce is the only path to peace and prosperity.
He describes commerce as "swindling each other", enjoys watching yacht races, is two metres tall and "globular" in shape, has a goatee beard, dresses in colourful and anachronistic fashions, wears numerous rings, and is known as "Old Nick" by his employees for reasons too obvious to mention. He routinely speaks in a loud, basso voice which Anderson often likens to the sound of a hurricane or avalanche, much as his physical bulk is often compared to a mountain or a Jovian planet. He is apparently impervious to personal abuse but is angered by stupidity, incompetence, prevarication and anything else that slows him down. He is rarely a viewpoint character. He has never married but has taken many mistresses and has at least two natural children: Eric Tamarin-Asmundsen, son of the Grand Duchess of the planet Hermes, and the unnamed mother of Coya Conyon, eventual wife of David Falkayn, van Rijn's most trusted employee and the other central character of the Polesotechnic League series.
He swears by a number of saints including Saint Dismas (the Good Thief, appropriately), and has expressed the intention of burning candles in offering (to which another character responded "Saint Nicholas had best get it in writing"). In times of stress, he has been known to shout "This I have not deserved! Do you hear me!" at the sky, presumably at God. It seems possible he is Catholic.
Anderson may have derived the name from the famous painter Rembrandt Harmenszoon van Rijn. Other famous van Rijns, however, have existed. The prefix van, unlike the German von, is not an indicator of minor nobility.