Second time around this book is still weird. Overall I liked it, but not as much as the Culture novels that I've read. The characters just don't have as much texture and the whole universe feels like there's some back story missing, sort of. Some elements don't seem to really tie in, either (e.g. the Truth).
Most of the initial scenes with Luseferous don't actually add anything to the book other than maybe
making his character less of a shock later on in the book (and by that I mean they make him more credible because it's not coming completely out of nowhere). Or maybe you've just gotten used to his over-the-top-ness. Even then I think you could cut out his early scenes entirely. Oh, and I still can't entirely believe they stopped along the way.
I did like the Dwellers and the AI, however. There's just something endearing about aliens that call to mind exuberant big-game safari hunters.
I haven't figured out what actually gave the gardener away, and I seem to recall the zero-answer being a bigger puzzle and happening earlier in the book the first time around. Apparently I can't trust my memory.