which is good objective book to start maths jee preparation? is universal self scorer errorless maths is good to start?

Yaa it's fine. At the end of the day you have to build concepts well in your head.

Many people will suggest you to go for Rd sharma objective. Its a good book no doubt but it's not complete. What I meant to say is the questions are not enough and you will have to practice more questions + tricks. Next book is "Resource Book in Mathematics for JEE MAINS" by "Prafull K Aggarwal" . Every person you ask will suggest you this book. I don't know whether they have used it or not but I have used it. First of all the book has misprinted information everywhere. So you will need to keep a standard book side by side to verify the formulaes. If you go to coaching then you will be easily able to catch the misprints and mistakes. It's a good book with questions from NCERT + Examplear + Archives of JEE main. The biggest problem with this book is that the theory is not sufficient and there are lots of direct formulaes given which you will have to simply mug up because book doesn't mention how the formulaes were derived so good luck remembering formulaes in exams. Also, examples given is not sufficient for one to grasp the concept.

The last book I used is cengage. This book has all you need . It has the best theory along with lots of illustrations . Yes, the book reads advance but it has plenty of objective questions(upto JEE main level) which if you solve will be enough. My advice will be to buy cengage and practice questions from MRB as much as you can and gain mastery. See, no book can guarantee you success if you don't grasp the concepts and know how to apply them . Cengage is the only book I have used which has lots of illustrations over every concept. Cengage is best book according to me.

Best wishes. Thank-you.