Yes, investing 6-8 hours per day is a good start for UPSC preparation as a beginner. However, it is important to have a structured and comprehensive plan to cover all the UPSC exam topics.

Here are some steps you can follow to prepare for UPSC:

1. Understand the UPSC exam pattern and syllabus: Before starting your preparation, make sure you are well-versed with the exam pattern and syllabus.

2. Create a study plan: Create a study plan that is realistic and achievable. Divide your time equally between all subjects and allocate more time to the topics you find difficult.

3. Refer to standard UPSC preparation books: Refer to standard books for each subject recommended by toppers and experts.

4. Read newspapers and current affairs: Stay updated with the latest news and current affairs. Read newspapers, magazines, and watch news channels to stay informed.

5. Practice writing skills: Writing skills are important for the UPSC exam. Practice writing essays, answers to previous year question papers, and take mock tests to improve your writing skills.

6. Join a coaching institute or online course: Joining a coaching institute or an online course can help you get a better understanding of the exam and provide guidance.

7. Revise regularly: Revision is important to retain what you have learned. Revise regularly to avoid forgetting important topics.

Remember, consistency and determination are key to cracking the UPSC exam. Keep yourself motivated and focused on your goal.

In conclusion, the UPSC Bible: 15 Steps to Clear UPSC CSE by Toppers (ranked under AIR 100) can be a good reference guide for UPSC preparation. However, it is important to supplement it with standard books and current affairs updates.