What is the meaning of take approach in this sentence?
Most books take a very low-level approach, teaching you how to use individual classes and accomplish fine-grained tasks.
Taking an approach means selecting the direction from where you want to start solving a problem.
For instance, I could find myself wanting to teach someone a language.
I could start with just vocabulary, or I could start with grammar.
Those options could be described as a "vocabulary-first approach" or a " grammar-first approach".
Approach comes from the verb approach which means moving closer to a goal. When there are several directions from where to reach that goal, I have the choice of several approaches.
The word is also used in a more literal sense, for instance when an air plane is going to land, it approaches the airport. When it is lined up with the landing strip, and it descends to actually land, we say it is on final approach.
A moment in time can also approach: the end of the month is approaching as I write this.
In your sentence, the word is used in a figurative way. There are supposedly several ways to accomplish what you want to accomplish, and most books take a specific direction to get there.