There are several books available in the market that provide explanations for previous years' question papers of the IIT JAM Physics exam. These books are designed to help aspirants understand the concepts and techniques required to solve the questions effectively. Here are some popular books that offer such explanations:

1. "IIT JAM Physics Solved Papers and Practice Sets" by EduRev:
- This book by EduRev is specifically designed for IIT JAM Physics aspirants.
- It contains detailed explanations for the previous years' question papers, helping students understand the step-by-step approach to solve each question.
- The book also includes practice sets and mock tests to enhance the problem-solving skills of the students.

2. "Solved Papers & Practice Sets IIT JAM Physics" by Arihant Experts:
- This book by Arihant Experts provides comprehensive solutions to the previous years' question papers of IIT JAM Physics.
- It includes detailed explanations for each question, along with the relevant formulas and concepts.
- The book also offers additional practice sets and sample papers for thorough revision.

3. "IIT JAM Physics (Solved Papers and Practice Sets)" by Disha Experts:
- This book by Disha Experts includes solved papers of the IIT JAM Physics exam from previous years.
- It provides detailed explanations for each question, helping students understand the underlying concepts.
- The book also offers practice sets and mock tests for ample practice.

4. "IIT JAM Physics: Previous Years' Papers (Solved)" by R Gupta:
- This book by R Gupta contains solved papers of the IIT JAM Physics exam from previous years.
- It provides detailed explanations for each question, ensuring a thorough understanding of the concepts.
- The book also includes practice questions and sample papers to help students prepare effectively.

In conclusion, these books mentioned above are some of the popular options available that provide detailed explanations for the previous years' question papers of the IIT JAM Physics exam. Students can choose the one that suits their preferences and study accordingly to enhance their preparation for the exam.