Since this is asked in engineering I will answer from the perspective of jee. 

Jee was designed to test what you learned in 11-12th physics chemistry and maths. This was done as 12th board exams test your ability to learn while jee tests your ability to apply what you have learned. 

So, there are many successful jee aspirants who go through 11-12 books completely and then use this knowledge to solve jee questions. 

My suggestion to you would be same, learn 11-12 course material thoroughly then use one of the resources available to apply your knowledge. 

Hope this helps.