Hello!

It may not appeal to you but the NCERT books starting from VIII standard and going up to XII are very important resources and fall under the category of 'must read' in order to crack UPSC. The topics you should cover from these NCERT books are ancient history(NCERT Class VI and Rs Sharma XI), modern history(NCERT Bipin Chandra Class XII), polity(NCERT XI and XII), economics(NCERT XI and XII, Macroeconomics), geography(NCERT VII, X, XI, XII), environment(NCERT VII and XI) and world history(NCERT story of civilization vol 1 and 2).

Apart from this, you can refer any good coaching material to cover up the general studies. You can also refer to leading newspapers for current affairs part.

You can get an elaborate guide about UPSC preparation using the link below:-

https://www.google.com/amp/s/competition.careers360.com/articles/how-prepare-for-upsc-ias/amp

Hope this helps!