I used to grow kombucha. (Juniper -- it's sometimes called a mushroom but it's actually more like a culture, I don't know what the organisms are in particular, but the liquid tastes a lot like cider vinegar. The liquid is said to be a miraculous tonic for everything.)
I actually enjoyed the process a lot. It was kind of like my first pet. It's really cool and amazing how it grows in your kitchen and reproduces, and you just use the byproduct. I don't know what the NT book says, and I'm going from memory, so let me know if I leave out stuff you need to know.
Start with the right equipment. (eg enamel pot, no chips or other exposed metal; wooden spoon; nice size glass jar for keeping the kombucha, etc.) About the jar -- it will grow to the width and shape of the jar it is in.
As I recall, you have to use black tea. I don't remember the formula for water/tea/sugar. I didn't want to use sugar but the recipe I had said not to substitute. I wonder what NT says on this? . . . Really all you have to do is make the tea, let it cool, strain the liquid off the komb. and replace it with the new batch of tea. Then the hard part. Find someone who wants to have kombuchas and give them the new/second one. You have to do this every 7-10 days.
The primary reason I quit doing it was that I repeatedly had to throw out batches because they got moldy. (Years later the building had a major mold problem and I got really sick. I didn't know before then that mold can be dangerous. But looking back I suspect the building was sick long before I knew and that's why the kombuchas always molded.) If this happens, you will know. A good batch does not taste bad, like I said it's a lot like cider vinegar. (I guess some people would think that's bad, I didn't find it unpleasant at all.) If it tastes horrible or bitter, throw it out.
I don't know where to get a kombucha to start with. Do you?