Book #23 - Wizards and Glass by Stephen King.
This has definitely been my favourite of the series so far, I really enjoyed Roland's backstory as a freshly minted gunslinger, out in the wide world, and his meeting of his love Susan. Obviously I knew it was going to end badly, but I thoroughly enjoyed the story as it unfolded. To me all the characters in Mejis felt more fully actualized than either Eddie or Susannah, and I resented it whenever we made a brief interlude to go back to that bunch. It was very important to meet Susan, Cuthbert and Alain (again for the latter too) as this story does so much to humanize Roland. The western touches, the post-apocalyptic touches, the fantasy touches... they were all blended together quite masterfully...
Which made me really go WTF when we returned to the 'modern' ka-tet and they ended up in a parody of a well-known tale... it felt really heavy handed. I think if it had been a little more subtely presented (ie not all the characters going instantly 'oh we're in such and such), I might have enjoyed it more. Now, I'm not saying King's the most subtle of writers, he's not, but this felt clumsy even for him.
However, the awkward ending didn't diminish what I really did like about this novel, and I'm all for more Roland flashbacks in the future.