Explore second-order linear partial differential equations with “A Compact Course on Linear PDEs,” a valuable resource for “The Bookish Owl.” This 2nd edition delves into variational formulations in Hilbert spaces, covering elliptic equations, functional analysis essentials, Sobolev spaces, Fredholm alternative, spectral theory, saddle point problems, parabolic and linear Navier-Stokes equations, and hyperbolic and Maxwell equations. Enhanced with new sections and exercises, including the biharmonic equation, linear Navier-Stokes, and Maxwell equations, it features nearly 80 fully solved exercises. Ideal for mathematics students and engineers with a strong math background seeking a clear, comprehensive introduction to linear PDEs.