The Other Merlin by Robyn Schneider
This is a telling of the King Arthur story with modern sensibilities. Emry Merlin is the daughter of Merlin and has a twin brother. Her brother is supposed to go to the castle to be an apprentice wizard. However, he botches things up in an attempt to avoid a gambling debt. Emry goes there temporarily in his place. In the kingdom, things get interesting. Arthur and Lancelot are goofballs, with Arthur being a semi-illegitimate successor to the king. But then Arthur pulls the sword from the stone and later gets Excalibur. He now has the bonafides to be the ruler. Emry and Arthur also start to fall for each other (really confusing Arthur, who thinks Emry is a boy.) Eventually, he discovers the truth and they have a twist, only for Arthur's father to soon announce Arthur's engagement to another girl. Things get bad, and then get worse as a dark wizard attacks Emry. Arthur helps come to the rescue, and things get better, with Arthur standing up to his father and asking Emry to be the court wizard. The mix of modern sensibilities with historical settings does almost work, but requires a bit of suspension of disbelief. (If a gay knight and woman wizard are such a challenge to that society, it is not likely they would be so easily overcome.)
