1.Engineering Mechanics :-

Enginnering Mechanics :- by R.K. Rajput :-

This books contains all you need to know about the subject matter  in simple and lucid language .It also contains a large number of numerical problem.
Enggi. Mechanics by U.C. Jindal :-
This book has a simple language and problem solving approch. 

2. Strength of Materials:-

A.Strength Of Material by B.C. punmia:- 
This excellent book contains simple but complete covered of all the concepts related to the topic.A large number of the solve and unsolved example contains real life . This have the good for both concept and problem. 

3.  Theory of Machine:-

Theory of machine by S.S. Rattan :- 
 This books has you develop the concept in a simple the concept in a simple language. It is perfect for competitive exam like GATE and IES . this has the both good the concept and problem.

4. Mechanical Vibration:-  

Mechanical  Vibration by S.S. Rattan /G.K. Grover:-
  It is excellent book with clear  concept which make the subject interesting for the reader. This books is ideal foe beginner in Mechanical vibration . It is very suitable  and Reliable for GATE, IES and other competitive Exam. 

5. Machine Design :- MD by V.B. Bhandari / Shigley  Edition 3

Both books chapter is written in a simple language. V.B. Bhandari is in logical way, explanation the theoretical  consideration in the Design of Machine Element. V.B. Bhandari is perfact for the GATE & IES but shigleyis very good books for concepts.

6. Heat transfer  by R.C. Sachdeva / J.P. Holman:-

These books contains adequate theory and problem which are very much useful for GATE  preparation .
R.C. Sachdeva have you will make the concept very easy to  understand  but J.P Holman has large number of solve and unsolved example. So i suggest  both books.

7. Thermodynamics :- by P.K. Nag

This books is important  for make our concept and numerical problem . It is best for every various Examination.

8.Application of Thermodynamics 

Power plant Engineering by R. Yadav:- 

This books is a good and up to date  the on subject. It has detailed coverage on Hydroelectric, diesel engine, and gas turbine. 
 Internal combustion  Engine by  V. Ganesan / M.L. Mathur & R. P. Sharma
V. Ganesan is written in very simple way and all content are covered . It is fir beginner because the language is lucid. But the mathur & Sharma is very important for GATE & IES  Exam. So I suggest Mathur & Sharma .

refrigeration and air conditioning by C.P. Arora /R.S. Khurmi/ P.K. Nag

R.S. Khurmi is good books for beginner in the khurmi has the covered all basic concept . But C.P. Arora has the most books for the GATE & IES exam preparation. So i suggest for the GATE & IES  C.P. Arora. 

 9. Fluid Mechanics By  R.K. Bansal / Modi & Seth/ S.K. Som

These books contains a comperhensive treatment of the subject matter in simple , lucid and direct language and envelopes a large number of solve problem including typical example important form the examination point of view. 
Bansal is simple & up to work . Modi & Seth is good for clearing the  concept . S.K. Som is  book if you are good in development Mechanics &  Diffrential Equation. 

10. Production Enginnering :-

Material Science by I.P. Singh:- 
this is in simple licid and easy to understand so I prefering  the for GATE & IEs this books.
Manufacturing Process:- by the R.K. jain  
this is covered the most topic for the production enggi. so it is good for the GATE & IES.

11. Industrial Engineering :by O. P Khanna
This is comprehensive  books for undergraduate students Mechanical and  production Engineering . this books for GATE Mechanical  are quite helpful for student preparing for GATE 2019.
12. Operation Research 
*Operation  Research by Kanti Swarup / S .D. Sharma 
This books contain a series of  question and solve example to help evaluate  your strength  and work on them accordingly.