The book sounds like it could be The Truce at Bakura by Kathy Tyers. Wookieepedia quotes the publisher's blurb:
No sooner has Darth Vader's funeral pyre burned to ashes on Endor than the Alliance faces a new challenge at the far-flung Imperial outpost of Bakura. The Ssi-Ruuk, a race of cold-blooded reptilian invaders, plan to enslave human minds to pilot their invincible machines of war and destruction. With the hope of turning Bakura's loyalties toward the fledgling New Republic with defensive aid, Luke Skywalker, Han Solo, and Princess Leia race to the besieged planet. Yet as the eve of the final onslaught rapidly approaches, Rebel and Imperial forces still must come to terms with each other. And there is already evidence of a traitor hidden in their midst…
Woookieeepedia's synopsis has much more detail.
I suspect it won't be the basis for Episode 7, though (unless young Ssi-Ruuk are as cute and merchandisable as Ewoks).