Hhmm, yes .. but the main difference being that the characters were really really strong in TC, and shockingly poor (in my opinion) in Fionavar. It definitely wasn't the concept of TC that primarily spurred me on - it was the characters and the world (VERY Tolkien-esque) which I loved. Nothing "grabbed me" in Summer Tree, so much so that I gave up after about 100 pages, something I rarely do.