I've read many Baxter novels, so when I started reading this, it seemed apparent that it was an earlier effort. I could hear his Scottish accent throughout!
The idea is, if you'll pardon the pun, novel, and he fleshes it out fairly well. The characters aren't nearly as well developed as in his later attempts, which was, again, something that told me it was an earlier book, yet they were still quite good... fairly believable. His science is VERY hard in this book except for the MacGuffin -- the seed itself -- which is essentially unknowable, yet he tells what can be divined from it. There is a lot of action in the story, and he handles it more or less well, yet there was so much, that he couldn't spend a lot of time making all the scenes and situations as three dimensional as could be done. Yes, if he had, the book would have been 900 pages.
Overall, I enjoyed the ride, and didn't mind the length because I would much rather see all the interesting subplots resolved and have a long book, than leave them dangling just to save a tree or two. I think some people will complain about some of the overly technical explanations, and while I felt they were pretty lengthy even for hard-sf, I didn't mind even though it slowed the pace a bit. I mostly felt like he was just showing off. Kind of made me smile a bit.
So, I can easily recommend it, especially for hard-sf fans. But I hope I won't scare off anyone else; it's not like he's showing mathematical proofs or anything. Just think of it as well researched!