The "Not Synonymous" series is a BtVS/HP crossover. It is majorly AU both for BtVS (events took a right turn at Albuquerque beginning sometime around "School Hard" in Season Two) & for HP (for reasons which will become obvious in a hurry). HP's timeline is shifted so that its Book One/Year One begins a year after BtVS Season Seven.
Stories in the series are *not* being written in chronological order, nor do they necessarily need to be read in any particular order (though "Visit" actually does make a good starting point).
Chronological order of stories: Wish, Family, Visit
Categories: Harry Potter > Harry/Draco, Buffy the Vampire Slayer > Spike/Xander Characters: Angel(us)/Wesley, Buffy/Riley, Drusilla/Cordelia, Ethan/Giles/Anyanka, Harry/Draco, Spike/Xander, Willow/Tara/Oz
Genres: Alternate Universe, Crossover