1. According to demand of the world just now, which engineering stream should I prefer, Aeronautical or computer engineering ?

2. Which is the best book for practicing chemistry for JEE mains and Advanced ?

@ prachi 
1- that depends only upon your intrest , if u are intrested with mechanes , then go with mechanical engg , and getting comp sci engg are also not that much easy . 

but if u want agood salary package with high brand demand , then u must have to go for comp sci and engg . 
2- for chemistry u can follow the following books 
ORGANIC CHEMI BY MORRISION AND BOYD 
INORGANIC CHEMI BY BY GRB PUBLICATION 
PHYSICAL CHEMI BY P BAHADUR . 
HOPE IT CLEARS 
ALL THE BEST ..