Use drawer slides; mount the drawer on the wall; attach the shell to the slides, so it pulls out. Shifty Desk / Hallway Stand by Daniel Schofield This is such a great storage idea! It can be a shelf and a drawer.
Hold on Tight bookshelf. A brightly-coloured aluminum cube and oversized wing nut serve as a sliding bookend which can be adjusted and secured wherever it is needed, whether your book collection is growing or shrinking.