Hello Aspirant

The State Board of Technical Education and Training Andhra Pradesh, Vijayawada will conduct the Polytechnic Common Entrance Test. It is a state level entrance exam to get admission in diploma courses in engineering/non-engineering and technology offered at polytechnic institutions in the state of AP. Every year the number of candidates appeared in this examination and score well.

Your core focus should be on studying Science and Math of your high school level. If you are clear with these two subjects, then it is not very difficult for you to clear the exam. You can buy advanced books or guides for these subjects. You can also just follow the book you studied from in your high school. NCERT books are mostly recommended as a basic book to consider.

If you are still willing to study more for the exam, there are certain books that you can consider, such as

Ramesh Polytechnic C.E.T. Guide 

Upkars Practice Work-Book Polytechnic Combined Entrance Exam.

Arihant Uttaranchal Polytechnic Entrance Exam. Self Study Guide

Ramesh Diploma Engg. (Polytechnic) Guide 

Oswaal Chapter Wise Solutions Polytechnic Bhotik, Rasayan Ganit (Hindi)

Other than these books, you can simply type in Amazon, and search through the options available there. There are other stores also. 

You can visit the physical stores that sell books for such purposes and ask from the books that were sold the most that year. You can also buy the second-hand copy if it is available. 

There is no one specific book which is deemed as compulsory or to be the ticket to clearing the exam. It all depends on your knowledge of the subjects. You can also look for resources online, there are many websites that provide quiz and questions. There are also many platforms that provide crash courses or coaching for various exams, you can opt for this also. 

It all depends on your studying pattern and your level of commitment.

I hope that I have answered your questions and if you have doubts, then you can ask those doubts in the comments section.

Best of Luck!