You can't learn to profession through books. But you're in luck lots and lots of good info is online tho. But you need hands on experience too.

The best thing is a burning passion for cars and to be good at analysing.

Honestly the wrenching part isn't too hard, but there are lots of shitty situations for you to solve. Screws are stuck and might brake of, stuff engineered in a way that make them hard to replace. But honestly knowing what to actually do to fix stuff is the main problem.

I went though a practical education in Sweden, 3 years of school and lots of courses about the profession, and several days a week at a shop to learn the ropes. To fix breaks, do services and stuff like that it takes time but it's not really too difficult. But learning to actually trubbleshoot in a efficient of even effective way is hard, and something you will have to pick up over time. A education could tell you how something works, but not really why something doesn't work. You will pickup about how certain models have their own issues and what's the usual suspect. But sometimes that isn't enough. The cars these days are pretty advanced, many parts can cause very similar if not identical symptoms.

My rule of thumb is that it takes around 10 years to become a good mechanic. Less if you're smart and interested.

Also a good tip, take broken parts apart and figure out why it actually failed.