I'm not at all sure of this...but perhaps you are referring to one of the Psy-Changeling books by Nalani Singh.
The Psy-Changeling world is made up of three races:
The Psy have phenomenal mental abilities, from telepathy to telekinesis, psychometry to foresight. However, these gifts come with a price—they drive the Psy to insanity and murderous violence. As a result, at the beginning of the series, they have lived for over a hundred years under a protocol called Silence, which conditions them to eliminate their emotions. The Psy are cold, detached, and do not have relationships based in emotion. The most powerful among them are called cardinals. Cardinals are identified by distinctive eyes colored like the night sky – white stars on black.
The changelings have two forms—human and animal—and they are at home in both of those forms. Some changelings are dominant, others more submissive. Major changeling groups in the series include: leopards, wolves, bears, water-based changelings, and falcons. They are as emotional as the Psy are cold. Passionately devoted to their mates and blood-loyal to their packs and clans, changelings are physically powerful and as dangerously intelligent. An alpha changeling can go toe-to-toe with a cardinal Psy and not blink.
The humans are like you and me. However, they’re caught in the midst of the power struggle between the Psy and the changelings. At the beginning of the series, the humans are considered the weakest of the three races, but as the series continues, we discover they have a critical role to play. The Human Alliance is the group that represents human interests in the Psy-Changeling world.
The series is set up as a series of romance novels between Psy's and changeling referred to in the books as a shifter fairly often).
If I remember the first novel was a romance between a Psy and a leopard shifter. He has a treetop home.