I think this is the biggest age gap I've ever read in a book (22 yrs) but strangely it didn't bother me at all. Cooper was just so mature for his age, it was on a very rare occurrence that he'd do or say something that made him seem in his 20's. And Tom was pretty cool, too. Together they were just a cute couple.
The whole Architecture thing was really interesting too. It's not something I'd have thought would interest me but reading about the drawing of buildings and all the details that were needed...it was quite fascinating.
I'd definitely be interested in the rest of the series.