Thief of Time - pratchett
Anansi Boys - Gaiman

Both deal with a single entity split in two - one at birth, the other - I no longer remember. Something about Anansi Boys is very slippery, I always need to reread it because I forget.

Anyway. I randomly decided that the narrator was either unrequitedly in love with Gonzo or his split-off inner self. (I do admire Harkaway's use of the unreliable narrator here, however boring the narrator in question is.)

At the moment, what comes to mind in terms of explanations is Babycakes' explanation of corporate drones, their levels, and how they are made. I think we see it, in varying forms, at least three times in the novel. Each time it is very clever, but it is still the same information over and over. If I had been his editor I'd've said, Nick Harkaway, you are very clever, but most of your readers are going to either read very slowly or be quick enough to catch up with you on the second repetition. Save it for your next novel. Or blog. Or letter to your mum. Anywhere but here!