A pair of disposable latex gloves:  Not absolutely necessary, but good for keeping grease and grime off your hands during a repair.  Also, nice to have in an emergency when it starts raining and the temperature drops 20 degrees and you don’t have a pair of regular gloves.   Just keeping your hands dry and the wind from directly blowing on them makes a huge difference in comfort.
To pick the right size bicycle, you want to measure your height, and specifically your inseam (inside leg), in proportion to the size of the bike frame. The inseam measurement determines the seat height, or the “stack.” Next, you must calculate the “reach,” which is the horizontal distance between the bottom of the frame and the head of the bike -- or, in layman’s terms, the distance between seat and handlebars.
These guys are awesome. After work, I got to my bike to discover my back tire was completely flat. It had a slow leak, so I was able to pump it up enough to make it to their shop. I got there 10 minutes before closing and they were able to fit me in. They replaced my tube and picked all of the glass shards out of my tire. Awesome customer service and they saved me from having to do this myself in the dark and the cold.
This is a very basic book and unnecessarily repetitive in sections. It does introduce the reader to the basic nomenclature of bicycles and this is helpful when conversing with others. Unfortunately the repetitive sections were not replaced with chapters on 3 Speed in hub gear drives, or coaster breaks, or a chapter on Adult Tricycles and Tandems and E-Bikes.

Whether you ride a single, 7, or 10 speed bike or anything in between, you will need a slightly different chain. The major difference is that they come in varying widths to accomodate the different spaces between the gears, but quality of construction is also a factor in choosing a chain. Inspecing the chain should be a part of your regular cycle maintenance procedure- It’s important to keep a chain well lubricated, but oil will also attract dirt and so different oils for specific riding conditions are available. Remember to clean your chain regularly to get the longest life out of it and the gears.