The food lab by j Kenji Lopez alt is another cooking book (with lots of recipes) that really helps you understand why and what you are doing rather than just telling you a process to follow.
Highly recommend anything Kenji does (previously he was the main force behind seriouseats.com) and also does a lot of first person point of view cooking videos on YouTube where he explains why he is doing things while he is doing them.
Second that! He has a very scientific approach, sampling various ways (cooking dishes in six different ways, comparing them), which makes it far easier to understand why something is done that way.
Highly recommend anything Kenji does (previously he was the main force behind seriouseats.com) and also does a lot of first person point of view cooking videos on YouTube where he explains why he is doing things while he is doing them.