Hello Kamlesh,

I assume by Physics olympiad you mean NSEP(National Standard Examination in Physics) which is conducted by IAPT every year. The registration process for NSEP 2019 will begin in the first week of August and will continue till the third week of September.Aspirants can register via their schools or through the IAPT website. The exam will take place in the fourth week of November. Candidates who qualify NSEP qualify for the Indian National Physics Olympiad(INPhO) which serves as the screeniing for International Physics Olympiad(IPhO). 

As for your question, the books that are recommended are HC Verma volume 1 & 2 and IE Irodov for questions. Also solve the previous year question papers to get an idea of the problems. 

The syllabus is listed below:

Theoretical Skills:

• Mechanics
• Electromagnetics
• Relativity
• Oscillation and Waves
• Thermodynamics and Statistical Physics
• Quantum Physics

Practical Skills:

• Accuracy
• Measurement techniques and Apparatus
• Experimental Uncertainty Analysis
• Data Analysis

Mathematics:

• Algebra
• Functions
• Geometry
• Vectors
• Calculus
• Complex Numbers
• Statistics
• Approximate and Numerical Methods

Fo more information, follow the below link:

Https://school.careers360.com/articles/nsep-registration