Pocket-Sized Connection to Another Dimension

The protagonist accidentally discovers that his pocket connects to a hyperdimensional space, and begins to figure out how to use this ability... That's the general idea. The somewhat exciting parts don't really begin until at least a hundred chapters in, things get more interesting around chapter two hundred, and the climax, which is where the real story begins, is around chapter five hundred. I don't know if anyone will stick with me long enough to keep writing. See for yourselves if you're curious. The early part isn't much to look at.