I think I can easily say this is my favourite TNG-R book of the 4 so far (or 5 if Death in Winter counts). I've enjoyed all of them a lot, but whereas Resistance had me sighing with exasperation every few pages and Before Dishonor was full of awful, awful humour (particularly that unnecessary sequence with the 'peace in our time' ambassador), Greater Than the Sum had me smiling throughout.
Whether it was the introduction of the new crewmembers, Elfiki, Choudhury, the Bajoran counselor and T'Ryssa (who I personally thought was brilliant), the sudden appearance and development of Hugh and his Liberated, the incredible new lifeform or the addressing of basically every Borg loose-ends, I absolutely loved it. And marrying off Crusher and Picard? It's about time! And they may even beat the Trois to having the first senior officers' baby!
Speaking of crewmembers, I thought Christopher did a good job with T'Lana, Leybenzon and Kadohata. Okay, the semi-redemption of the universe's least popular counselor didn't evoke any sympathy from me, I was glad she was shipped out in a slightly more dignified fashion than she could have been. Leybenzon, well I never really liked him to start with so his role in the epilogue turned that grin I'd had on my face for the last few hours into a massive evil smirk. And Kadohata... well, I liked her anyway, glad her family/flirting was sorted out and now she's back to the likable lady she was in Q&A - fantastic!
I think the only question I have after reading it all is about Guinan. I know she's experienced with Borg matters and is a great friend of Picard and probably the best person to have his family vs career debates with, but was there any particular reason she wasn't brought back before GTTS? I don't mind that she's left again too much, it just seems a bit odd to bring back this classic TNG character for just one book.
So overall my favourite Trek book of the year so far, slightly edged above Fearful Symmetry. I expected nothing less from Christopher of course after Orion's Hounds but those expectations were shattered.
Finally, am I the only person who laughed like a idiot when the Borg appearred on the E's bridge and Picard, trapped between seats/consoles, thought "Bad bridge design..."?