To build a library wall DIY, start by selecting modular off-the-shelf bookcases that fit your space. Plan a layout that maximizes storage and balances style. Attach them securely to the wall, then unify the look by adding crown molding on top and painting the units a cohesive deep color. Finish with careful caulking and shelf styling. This project combines carpentry basics with design for high-impact built-in shelving.