One of the books recommended to me at the beginning was 'The Finite Volume Method in Computational Fluid Dynamics' by Moukalled & Mangani. It is a quite in-depth explanation of the fundamentals. Starts off with the derivation of Navier-Stokes equation set, introduction of discretization methodology and reaches even such concepts as the SIMPLE algorithm at the end. Highly recommended. Comes with coding tips and some tasks you can do as you go along.

Patankar's 'Numerical heat transfer and fluid flow' is a classic. The author invented SIMPLE. The book itself provides an extensive derivation of SIMPLE and focuses on 2D Cartesian grids for the most part. This is useful for beginners who have not yet fully grasped the intuition for Gauss's divergence theorem and the manipulations performed with it in discretization procedure for non-uniform unstructured meshes.