Research and Desire Books in Order

Research and Desire is the wild-card series in this group. Written as Katie Allen, it blends erotic romance, romantic suspense, and mad-science thriller energy into one connected run. The books were previously known as the Human Design series, which tells you a lot about the premise before you even crack one open.

At the center is a secret lab program that created or altered men for someone else's purposes. The books follow what happens after those men escape, hide, fall in love, and try to stay ahead of the people who still want to control them. That gives the series a built-in mix of chase scenes, hidden identities, government or lab intrigue, and very personal questions about freedom and personhood.

Experimenting with Ed begins closest to the human world, with scientist Claire and protective bouncer Ed getting caught up in research fraud and flight. Natural Selection moves to Darwin Bloom, a man with no safe past to return to, and engineer Tom Cooper. Chemistry With Calvin keeps the pressure on with a hero in hiding and the woman who sees through him anyway. By Aristotle's Anatomy, and its later edition Double Dose, the series is fully living in its strange, high-stakes corner, with a speech therapist kidnapped to a mountain hideout to help men who escaped the lab.

This is the boldest, most high-concept part of Ruggle's backlist.

Even with the supersoldier angle, the books are not cold. They are very interested in damaged people trying to build trust, learn desire, and claim a future that was never supposed to belong to them. Some stories are sweeter, some stranger, some much more explosive, but the through line is always escape, intimacy, and the hope of making a real life out of something broken.

If you like your romance a little bonkers, a little dangerous, and very connected from book to book, this series is worth a look. Go in expecting secret labs, people on the run, unusual heroes, and a tone that happily mixes suspense with heat and just enough science-fiction weirdness to keep things interesting.