The TeXbook

Painfully giving this 4 stars - this is a classic in the history of computing and typesetting, and very funny and well written. However, actually trying to follow along with it and create the examples in TeX isn't as efficient and as well designed as it could be (it doesn't tell you how to actually use the software, for example!). This is likely just a sign of the times, but is also a reminder that you should probably just use LaTeX these days...