At least a few of the authors listed in the Recommended Reading sidebar have written many other books in the genre.
For example, the three trilogies listed for Mercedes Lackey are all set in the world of Valdemar, which easily includes another dozen or so novels. The ones listed, however, are the best introduction to both the setting and the genre. (I've only read the "Arrows" trilogy, which all of the Lackey fans I know agree is the best introduction to the series, even though some of her later trilogies are better.)
Lackey also has a series of three books featuring the witch Diana Tregarde (Burning Water, Children of the Night, Jinx High
) that could form a model for a romantic fantasy game set in modern-day Earth.
Likewise, the Tamora Pierce titles given are just four of many books she has written in the genre, most of them set in the world of Tortall. (Of these I've read the Alanna and Kel quadrologies, but not the set listed in the BR book...yet.)
You'll also want to take a look at John Snead's developer's journal entry about the genre, which mentions a few other authors and influences. That can be found on the old Blue Rose site:
http://www.bluerose.greenronin.com/blue ... =54_0_15_0