Hi,

The Best books for Electronics and Communication Engineering DECE [LE] are subject-wise:

•Analog Circuit and theory- Sedra and Smith

•Electronics Devices- Neamen

•Digital Electronics- M.Morris Mano or Anand Kumar

•Control System- Nagrath

•Communication Systems- Simon Haykin

•Signal and Systems- Oppenheim

•Network Theory- A V Bakshi

•Electromagnetic Theory- Sadiku

•Microcontroller- Mazidi

•Microprocessor- Gaonkar

•Engineering Mathematics- B S Grewal

These are the standard books for each subject, you can also search for its free pdfs.

Hope this addresses.