Hello,

First of all there is no separate syllabus for IAS or IPS even all the 24 services included in recruitment through UPSC, there are three stages of exams such as prelims ,mains and interview, the post you get is dependent on the preference you have filled and the rank you secure in the exam,

The first stage is prelims which is MCQs based and it has two papers for 200 marks each, the second paper is qualifying by nature, the numbers of prelims aren't added in the final list,

Recommended books are as follows:

History ; NCERT Class XI and XII/India's Struggle for Independence by Bipin Chandra,For Indian Culture, refer art and culture by Nitin Singhania

Geography ;NCERT Class VI to XII/GC Leong's Physical Geography/World Atlas

Economics ; NCERT Class XI/Indian Economy by Ramesh Singh

International Relations & Polity ;NCERT XII Political Science with current affairs/Indian Polity by Laxmikanth

CSAT ;Verbal and Non-Verbal Reasoning by RS Agarwal/
M Tyra's Quicker Maths

You can refer the following books for four General Studies Paper;

GS I - For History , Class XI NCERT book with India's struggle for Independence by Bipin Chandra,India after Independence by Bipan Chandra,History of Medieval India by Satish Chandra, In case of Geography refer World Geography and Geography of India by Majid Hussain, GC Leong's Physical and Human Geography with NCERT Class XI book.

For GS II - Polity and International Relations , refer Indian Polity by Lamikanth,India's Foreign Policy by Rajiv Sikri

For GS III - For Economics refer Indian Economy by Ramesh Singh, read ARC report along with Economic Survey and Fiscal Budget.

For GS IV - For Ethics refer a book named Lexicon by Niraj Kumar, also you can go through study material of IGNOU.

If you want to get detailed syllabus of both the stages, it's best you access the official notification of this year at https://www.upsc.gov.in/sites/default/files/Notice-CSP-2021-Engl-04032021N.pdf (https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.upsc.gov.in/sites/default/files/Notice-CSP-2021-Engl-04032021N.pdf&ved=2ahUKEwjQh5K3vu7wAhVM7XMBHUCQAbQQFjAAegQIBRAC&usg=AOvVaw3h4ikqkKEtX3Gdb3VPsZHJ)