Unlike some other readers, I didn't find this episode of the Foreigner series to be disappointing in any way. In fact, so much happens (well, in a CJ kind of way, you understand; it's not like Star Wars) that I had to pause half way through for breath and understanding.
If you've read any of the previous books then -- it's a treat! You will not imagine what happens to Bren. Dear old cuddly Bren Cameron gets the shock of his life and his adventure just zooms off. I can't help it: I'm captivated by the whole series and this instalment seriously accelerates the action. If you haven't read any of the others then please, truly, do try to find them before you read Defender. You'll get so much more from it if you have absorbed all the earlier lessons and information about Atevi culture, and about Bren's development. Dive in at the deep end and you'll probably just splutter around, flailing for a while.
Banichi and Jago are indeed ace, as is Gran 'sidi. They're all scary people, too; well rounded and well defined. They don't suddenly leap out of character -- in fact the dowager behaves exactly as you'd expect her to. Interpersonal relationships bonded perfectly with realistic space action. What more do you want?
Me, I can't stop thinking in felicitous threes. Oh CJ, does this mean that Explorer will be the last? Surely not. Seven, or nine even, would be better than six...