- Merrill Skolnik, Introduction to Radar Systems. The canonical text. If you read one radar book, this is it.
- Mark Richards et al., Principles of Modern Radar. Three volumes (Basic, Advanced, Applications). Comprehensive and modern.
- George Stimson, Introduction to Airborne Radar. Beautifully illustrated, gentle, surprisingly deep.
- Bassem Mahafza, Radar Systems Analysis and Design Using MATLAB. Practical, code-driven.
- David Adamy, EW 101 / EW 102 / EW 103. A very readable series on electronic warfare and radar countermeasures.
- Charvat, Small and Short-Range Radar Systems. Build-it-yourself radar from a former MIT Lincoln Lab engineer.
For current research, IEEE Transactions on Aerospace and Electronic Systems, IEEE Geoscience and Remote Sensing, and the IEEE Radar / EuRAD / IRS conferences are where the front line lives.
Welcome to radar. It is the most demanding RF system most engineers ever build, and it has enough open problems to last several careers.