Is it mandatory to maintain books of account who declare his income under 44ADA?

No, books r not mandatory u/s 44ADA

However you have to keep records for Receipts , Cash balance, Debtors Creditors etc for filling in ITR 4 - financial Information schedule

 

 Books of accounts/accounting records have to be maintained if the gross receipts are more than Rs. 1,50,000 in 3 preceding years for an existing profession. This also applies to a newly set up profession whose gross receipts are expected to be more than Rs 1.5 lakh.Then in your case Books of Accounts is required to be mentioned.

 

 

As replied by me above, books of accounts are not required to be maintained under 44ADA

Kapadia pravin you are right. under section 44ADA books of account is not required to be maintained if your gross receipt is less than 50 lakhs and declare your net profit more than 50% of your gross receipt.
you can maintain register for cash and cheque details for safety purpose. otherwise no need to maintain anything...enjoy