[Lioness]

Perhaps if Susan had survived, he would've succeeded that time around. He loved her, not quite the same kind of love that he loved Eddie, Jake, Susannah, and Oy with, but probably much mroe intense and blinding.

I didn't love the ending, but I didn't hate it either. I did feel like it was the only thing that could've happened, and it does make sense.
Perhaps next time he will save his friends, and instead of leaving them, he will climb the Tower with them. perhaps not though. Perhaps instead of skipping some rooms in the Tower, he will look into them all, discover something about himself that he didn't know before, and perhaps would make him worthy of not having to complete the journey again, and again.