Mind Games was good, light fun. I always enjoy telepathy stories; in this one, the heroine's ability was vastly magnified when she was sexually aroused, and she uses her ability to find her missing sister. The solution to the mystery interested me, and I would have loved to read more about those characters and what they were up to, but the mystery was subordinate to the rather sweet romance. I particularly liked that in the scenes at a swingers' club, the attendees were portrayed as realistic individuals who were enjoying themselves and not taking themselves too seriously, not the usual "everyone is slim and beautiful and elegant" mode that one usually gets in such depictions.
The Siren and the Sword was my favorite of the two. It's first in the "Magic University" series, which is Tan riffing on Harry Potter but in a university setting, in this case Harvard. The magic university, Veritas, is hidden among the Harvard buildings, invisible unless you have Sight. I would call it fantasy with romantic elements; it's clear that the protagonist, Kyle Wadsworth, will have a variety of romantic journeys in the four books. There are various same-sex couples as well as heterosexual couples, and eventually one character is revealed to be transgendered.
The mystery plot was much tighter and more involving to me than in Mind Games; it involves mysterious attacks in the library on students who've lingered after closing time. The mystery is wound in with Kyle's first experiences of the magical world; he comes to Veritas accidentally, and is still learning what skills he possesses.
I was amused that one character, Frost, was a distinct homage to Draco Malfoy from the Rowling books, and another, Quilian Bell, has echoes of Severus Snape.
Like Mind Games, it's a fairly short novel, so it was a pleasant weekend afternoon's reading. I'm really looking forward to the rest of these.