An analysis of the previous GATE Papers suggests that the following topics are relatively more important for preparation in Mechanical Engineering. Here, it may be noted that ideally one should complete studying as per the GATE Syllabus.
One should never leave things to chance but if emphasis has to be given, the topics given below can be considered as slightly important to merit more attention to their preparation. Alongside, we have also listed the books that can be used for studying these topics. Please note that the topics mentioned below are not placed in order of priority.
Topics - Books Recommended
Engineering Mechanics — Engineering Mechanics by Bhavikatti, Engineering Mechanics by Beer and Johnston, Engineering Mechanics by R K Rajput
Strength of Materials —— Strength of Materials by Gere & Timoshenko
Theory of Machines — Theory of Machines by Ratan
Design of Machine Elements —- Machine design-V.B. Bhandari
Strength of Materials —- Strength of Materials by Gere & Timoshenko, B C Unamia, Sadhu Singh, Ramamrutham
Fluid Mechanics —- Fluid Mechanics by R K Bansal, Fluid & Hydraulics- Modi and Seth
Thermal Science —- Mathur Sharma, Engineering Thermodynamics by P.K. Nag
Heat Transfer —- Heat and Mass Transfer by J P Hollman and R C Sachdeva, Heat Transfer by Cengel and Holman
Manufacturing Engineering —- P N Rao, Amitabha Ghosh and AK Mallik
Industrial Engineering —- Industrial Engineering by O P Khanna, Buffa and Sarin
Vibrations —— Mechanical Vibration by Grover
Thermo Dynamics —— Engineering Thermodynamics by P K Nag and Rajput, Thermodyanmics by Cengel.
I will suggest to follow the text book that you are most comfortable. The main thing is to be clear your fundamentals before appearing for any exam. The above mentioned topics are just for better preparation. It is highly recommended that aspirants should study the complete syllabus in detail rather than just a few topics. Since there is still ample time for good preparation for GATE, candidates should cover the complete Mechanical Engineering GATE Syllabus.