Spirit Runner, by Leon Southgate

A tale of multiple dimensions, secret government psychic agencies, off-planet humans and space-creatures. Our heroes are two psychic, disabled teenagers who can shift between dimensions. Long ago the world was consumed by the deadly space creature, the Elif. The government is in league with the Elif and everyone is determined to gain the ruro – the most powerful psychic substance in the universe.
The secretive psychic agency, the deadly, planet-killing Elif, even the good guys – everyone wants the psyche-enhancing ruro and the total power it confers. Unfortunately for Danny, everyone needs him in order to get it.
All Danny wants is a quiet life, a body that actually works and a girlfriend. The last thing he wants to be is an inter-dimensional hero..