As a part of my larger trip traveling around Japan, I wanted to make sure to stay at least one night in a capsule hotel, to have that experience.
I wasn't completely sure what to expect, but BookTeaBed was great. I had some trepidation about shared showers or bathrooms, but both were lockable cubicles that gave you total privacy.
The beds themselves were snug and comfortable. You had a locker in the hall by your bed for a bag, which was suitable for a backpack or carry-on-size suitcase (not a check-in size suitcase), and a small lockable cubby inside your bed pod for personal valuables.
If you're traveling light enough that you can stow your belongings, I would say you'd get a lot out of the flexibility and affordability of a capsule hotel like this.
BookTeaBed's selling point about books (it's in the name) is that there's a selection of books to read arranged on shelves across from each wall of beds. There was a lot of manga to choose from, much of it in Japanese (I'm early on learning the language, so I tried to read a little).