Hey as per my idea ISRO is Indian Space Research Organisation, and here I am giving you its basic details

Nationality
Candidate should be Indian

Qualification
The candidate must have complete the bachelor degree in engineering field
The candidate should have 60% aggregate
The candidate can also appear in the written test during the final year of bachelor degree.

Age limit
The candidates age should not be more than 35 years..
For SC/ST the age relaxation is 5 years and for OBC the age relaxation is 3 years..

Here I am suggesting you some books for ISRO Entrance Exam
DRDO, ISRO: Previous Solved Papers: Mechanical Engineering
BSNL DRDO ISRO: Electronics Engineering: Previous Solved Papers
Mechanical Engineering ISRO-SC/ENG Solved Papers (Thermal Engineering Book 1)
ISRO Recruitment Entrance Test For Scientists / Engineers In Electronics Paperback – 2015

Selection criteria
Written test
Interview