Hello Aspirant,

It is advisable to use NCERTs for preparation of JEE main 2019 as the questions are usually cocepco based and are less oriented to difficult numericals. Ncert will help you get a strong and coherent grasp of the concept plus it'll help you secure vettbe marks in certain sections of the paper. Cengage is not a bad book either but you can use it to solve model questions along with some previous years mains questions. Cengage provides a very nice collection of questions that is very helpful for preparation of JEE Mains special because of its exhaustive questions collection.

All the best.