Enthusiasts in any field like to play around with their tools or toys. Until recently, this was very hard to do with unicycles as there were very few choices of parts you could actually buy that would fit and work.
As has been mentioned, RSU is a gathering place for the enthusiasts, and many of them like to custom build, design, tweak, and share their results. Even better, some of them actually make production runs of their ideas, and the rest of us can buy them from places like Unicycle.com. What a great service!
But the vast majority of unicycle owners buy them off the shelf, and ride them the way they came.
As for stuff in print, there is On One Wheel, the newsletter of the Unicycling Society of America. It’s up to date in the fact that it comes out quarterly (www.unicycling.org/usa). You should be a member. But it’s not a book, and it doesn’t focus on equipment and parts.
All the books on the market are either a few to many years old, and predate today’s wide variety of parts and cycle choices. But what’s in them is mostly timeless, and they are valuable resources. The most “complete” one is called The Complete Book of Unicycling by Jack Wiley. It’s also available through the Unicycling Society of America.
The world could use a new unicycling book. Hmmmm.
I’m interested in the parts discussions, to some degree, but I’m not real interested in experimenting with my unicycles. I’m happy to let someone figure out a new solution, and then buy what they came up with. Otherwise, I’ll find someone locally to weld me what I need, such as an unbendable and non-flexing seat post for the Miyata seat on my MUni. But mostly, I’d rather have someone else figure out the solutions, then bolt them onto my cycle so I can spend more of my limited time riding.
How does one know how to customize a unicycle? By reading here. Use the powerful search feature to find enough parts discussions to make you puke. Normally, you would get together with fellow unicyclists to see what they’re doing, but we are pretty spread out, so this may not be a viable option for you. This forum right here, and muniac.com, are the two places with the vast majority of customizing information.
But wait a minute, you live down the street from Dan Heaton and John Childs. You’re in a unicycling mecca! So you could hook up with lots of local riders if you want.
If you are trying to figure out what type of unicycle is best for a specific activity, read the “Education” section on Unicycle.com for a brief overview of the main unicycle types. Beyond that, you make adjustments to a given cycle to enable you to do the activity better.
For example, in racing, you want your unicycle to be as light, narrow, and stiff as possible. Beyond that, it has to fit with the requirements for racing (wheel size and crank length).
And yes, much of the customizing is about art and the love of the unicycle. Technique goes way farther than a certain seat post. A good rider on a bent-up piece of junk can usually outride an average rider on the latest, most expensive hardware.