David A. Cox "Primes of the Form $x^2+ny^2$: Fermat, Class Field Theory, and Complex Multiplication." has a very good (at least to me, and many) methodology. He starts from page 1 asking a simple question, and then he builds a whole machinery to answer it. And to be precise here's what he says page 1:
This leads to the basic question of the whole book, which we formulate as follows:
Basic Question 0.1. Given a positive integer $n$, which primes $p$ can be expressed in the form $$p=x^2+ny^2$$ where $x$ and $y$ are integers?
We will answer this question completely, and along the way we will encounter some remarkably rich areas of number theory.
I think such way is extremely great, it gives the person the motivation to continue the whole book just by the existence of that basic question. So Are there any books in the spirit of David A. Cox "Primes of the Form $x^2+ny^2$: Fermat, Class Field Theory, and Complex Multiplication." ?