For the reasoning section in the RRB Group D exam, the most recommended book is "A Modern Approach to Verbal & Non-Verbal Reasoning" by R.S Aggarwal.

this book contains:

• Comprehensive coverage:

It covers all important topics of verbal and non-verbal reasoning, including analogies, classification, coding-decoding, blood relations, directions, series, etc.

• Explanation with examples:

The book provides detailed explanations with numerous examples for each concept, making it easy to understand.

• Practice questions:

A large number of practice questions with varying difficulty levels are included to help you hone your reasoning skills.

Other options for reasoning preparation for Group D:

• "Analytical Reasoning" by M.K Pandey: Another popular book with a focus on analytical reasoning skills.
• "Test of Reasoning" by Edgar Thorpe: This book offers a good mix of theory and practice questions.

GOOD LUCK!!