Tao is an alien stranded on Earth, engaged in a desperate battle against another faction of his own kind, to find a way home. But the only way these creatures can survive on our hostile planet is to be hosted by a native life form, preferably human. When Tao's human host is killed, the alien has to find another one before he too dies. Searching frantically, he finds Roen Tan in the nick of time. But Roen is an overweight, under-achieving slob. Tao needs to train Roen to survive before Tao's enemies catch up with them.
This is a pacey "alien mind-controls human host" caper, as Roen learns martial arts, guns, and spycraft. However, it doesn't add anything particularly new to the sub-genre that includes Hal Clement's Needle, F. Paul Wilson's Healer, and Jeffrey Carver's Chaos Chronicles series. The interaction between the aliens and their humans, Tao teaching dating tricks to Roen, the backstory of the aliens on earth affecting most of its history, and the denoument, are well-enough written, but ulitmately unsatisfying. A good book to read on a plane. (Note: the author appears to think that Dublin is in England; I would advise him not to visit Dublin in that case!)