Build an easy, portable 3' x 8' wooden bookshelf in about 20 minutes, with a minimum of tools and less than 1% waste, for about $60. The basic concept can be modified to create any size shelf system needed.
For a similar bed see: https://www.instructables.com/id/Cheap-easy-low-waste-platform-bed/
For a similar dining table see: https://www.instructables.com/id/Cheap-easy-low-waste-trestle-table/
As a professional carpenter, furniture maker, and designer/builder, I see a lot of home carpentry projects that are grossly overbuilt and over-engineered. One of the goals of this Instructable is to avoid the unnecessary overbuilding that I frequently see on this site, and that I see every day working in the residential construction industry. Many of the building methods we (in the US) use today are horribly wasteful despite the advances that have been made in materials science and structural engineering, because most people in the residential building industry, from architects and engineers to carpenters, are mired in tradition, doing things a certain way "because that is how it has always been done", rather than consulting the best available science, or even questioning their own assumptions about "the right way to do it". I don't intend to knock tradition, either. Many of the tricks, techniques, and tools that I use daily are definitely "old-school", but seem to have been forgotten.
Thanks to my father for introducing me to this style of shelving, and who built a particularly fine example (using stained fir 2x4s and 2x12s, black washers, and brass acorn nuts) which is at least 25 years old and still in use.