With our sons moved out, we're re-purposing rooms. My new study has a long wall that is begging for bookshelves and my collection of Arthurian Legends books needs to be displayed again. After building closet built-in bookshelves where I played with colors and making some new shelves in the kitchen where I used cherry plywood with stain and polyurethane, I've been tempted to give it a try in my study.
Look at the picture below from the excellent Home Depot DIY page on building shelves.
Well, you get the picture. A full day would be spent doing what a machine does in a few minutes. If I use inexpensive materials, I might come out a little bit ahead in terms of dollar costs, but the wasted labor hours would instantly obliterate any savings. Unless I plan to use materials like cherry and make shelves that are top-notch, I'm wasting my time building these myself. I'm a complete amateur at woodworking, so top-notch is out of the question unless I plan to spend a lot of time re-doing work that ends up sub-par.
Buying pre-made bookshelves is definitely the answer. If I want different and funky, I can always go to a consignment shop and get some antiques.