Tsubasa: Reservoir Chronicle 08: 09/03/15
Tsubasa: Reservoir Chronicle 08 by CLAMP has a journey to two different worlds: one which is a comedic interlude and the other which sets up the next big arc and reveals more about the villains.
Although the first story is there mostly for comedic reasons, it does reiterate the theme of dream vs. reality. There are cute fuzzy bunnies under attack from a whirlwind. It's Sakura's chance to shine.
Most of the book, though, is the introduction of the land of Shara where dual gods demand the attention of feuding groups. There is a troupe of performers, all women, who take in Sakura and Syaoran. Syaoran must dress the part to stay. Meanwhile Fai and Kurogane are found by a temple that houses the other god.
This plot demands extra attention when reading it (or when watching the anime). Yuko also intervenes, taking definite sides against the other dimensional witches (for lack of a better way of describing them). The most interesting thing to come out of it is that Mokona's travels from world to world haven't been as random as first thought.
For this book I suggest reading the translation notes. I would hope that you always read them, but if you don't normally, make an exception and read them. A lot of the nuances of the Land of Shara are explained there.