"Gaudy Night" by Dorothy Sayers.

I really like her heroine. Every forward and afterward declares that Harriet Vane is unlikable. She's sarcastic, unemotional, and leaves Lord Peter hanging proposal after proposal. She's favors intellect over feelings. She's quite intelligent and very witty. She and Lord Peter play quotation games in nearly every conversation. She also has occasional urges to write poetry. What's not to like?

This time around she's investigating a poison pen letter writer at a fictitious college at Oxford. Ironically, Magdalen college is mentioned fairly frequently. (Really, that's not glaring to anyone who knows the University well, but that's the college where C. S. Lewis taught.) I highly recommend anything by this author. This book is especially good for character. It doesn't have quite enough of Lord Peter. That works very well for the twist at the end. More humor comes from a group of single woman academics sniping at each other as tempers rise.