Midway through the series, Lord Peter meets a detective novelist named Harriet Vane. He falls in love with her immediately; the fact that she is on trial for murder is a secondary concern. Harriet, though, is not as easy to romance as Lord Peter would like, and he spends the next several years pitching woo in vain. But ultimately, Harriet does come around, in Gaudy Night, my favorite book in the series. The mystery is really kind of secondary-- it's worth reading for the vivid portrait of academic life at Oxford in the '30s, and of how women in the time struggled to choose between love and work and the scholarly life. Watching Harriet come to terms with these things makes for a totally fantastic read.
Naturally, I made a Harriet Vane Etsy treasury. I mean, wouldn't you?
what harriet vane would wear: an etsy treasury