Yes, there are books available that include previous years' papers for Mechanical Engineering Optional subject. These books are designed to help candidates preparing for the UPSC Civil Services Examination, specifically for the Mechanical Engineering Optional subject. These books serve as valuable resources for understanding the exam pattern, the types of questions asked, and for practicing with actual previous years' papers. Here are some popular books that include previous years' papers:

1. "UPSC Mechanical Engineering: Previous Years' Papers (Solved)" by GKP:
This book contains a compilation of previous years' papers from the Mechanical Engineering Optional subject. It includes solved papers from the last several years, providing candidates with a comprehensive understanding of the exam pattern and the level of difficulty. The book also provides detailed explanations for the solutions, helping candidates to grasp the concepts effectively.

2. "Mechanical Engineering: Previous Years' Papers (Solved)" by Arihant Experts:
This book is specifically tailored for candidates preparing for the Mechanical Engineering Optional subject. It includes solved papers from previous years' examinations, enabling candidates to gauge their preparation level and identify areas that need improvement. The book also provides explanations and key points for each question, making it a valuable study resource.

3. "UPSC Civil Services Mechanical Engineering Previous Years' Papers" by Disha Experts:
This book contains a collection of previous years' papers from the Mechanical Engineering Optional subject. It includes both objective and subjective type questions, covering various topics and subtopics of the syllabus. The book also provides detailed explanations and solutions for each question, helping candidates to understand the concepts thoroughly.

4. "Mechanical Engineering (Objective Type) Previous Years' Questions" by EduRev:
This book is exclusively designed for candidates appearing for the Mechanical Engineering Optional subject. It includes a vast collection of objective type questions from previous years' papers. The book covers all the essential topics of the syllabus and provides detailed solutions for each question. It also includes practice sets and mock tests to help candidates assess their preparation level.

These books are widely available in both online and offline stores. Candidates can also find these books on the EduRev website, which is a trusted platform for study materials and resources. It is important for candidates to thoroughly practice with previous years' papers to enhance their problem-solving skills and increase their chances of success in the UPSC Civil Services Examination.