Signals and Systems by Tarun Kumar Rawat is a comprehensive undergraduate textbook published by Oxford University Press . It is highly regarded by students for its "student-friendly" approach, often recommended for GATE and ESE aspirants who find more advanced texts like Oppenheim difficult to navigate.
While other books separate Laplace from Fourier, Rawat shows how Laplace generalizes Fourier for unstable systems. The Region of Convergence (ROC) charts in this PDF are particularly famous for their simplicity. Signal And System By Tarun Kumar Rawat.pdf