The Xander years Vol. 1 - Keith R. A. DeCandido

Having a Y-chromosome in Sunnydale is never easy. But Buffy's friend Xander seems to find more than his share of trouble with the opposite sex.
At first he is happy to attract the attention of the sexy new science teacher - until his schoolboy crush brings out her true animal instincts. Then his whirlwind romance with the exotic foreign exchange student falters when she demands the ultimate sacrifice. After that, you'd think he would have learned a thing or two. Besides, some members of the Slaying squad might say that dating Cordelia Chase could kill a guy. But Xander's relationship with Cordy seems to be working out - until she decides he's seriously harming her social standing, and his spellbinding plan to win her back looks set to earn him more love than one guy can handle.