Re; Adam Roberts, read a few of his books, and most are very good, one of the most common words you'll read on the cover reviews is high-concept.
I enjoyed ON especially, just because i'd never read anything like it before, basically it's a world which has gravity running slightly askew(all i could think was that gravity ran around the planet instead of in towards the core)*, one review said a world tipped on its side, so peope have to live on the sides of mountains, and if you fall off god help you.
I also thought Salt was great, as was Polystom the only book i've struggled with was The Snow another great premise to a story,a simple snowy day followed by another,and another,and another,you can see where this is heading.......etc,until the planet is covered under 3 miles of the stuff, and it's a good book at the start, it just got a little boring for me about a third way through, no doubt i'll pick it again one day.
can't comment on Gradisil.
I'm sure i read somewhere that Adam Roberts wanted to write a novel on every sub-genre within the genre itself,that could be quite a few.
*Im no scientist you know