If one were to learn more about the $P \stackrel{?}{=} NP$ problem, where would one start?
I understand what the problem is—but not enough to be able to read anything technical about it. Furthermore, I don't know where to start. When reading "This problem can be solved in $n^k$ steps" I only have a vague clue about how one goes about rigorously proving a statement like that.
Would getting an introductory book in something like boolean algebra be of use? Or should one focus more directly on computational complexity?
You should get a book on theoretical computer science, which will cover at least formal languages/automata, computability, and complexity. Sipser's "Introduction to the Theory of Computation" is widely used and a good place to start. From there you can start picking up auxiliary resources depending on what you have a hard time understanding.
A MOOC course might also be helpful. Here's UDacity's Intro to Theoretical Computer Science