I typically read about 80-100 books a year and while I'm now pretty well switched over to e-books, I still have a ton of paperbacks. So I decided to create some custom bookcases sized just for paperbacks. But I didn't want big, heavy pieces of furniture that take up lots of space so I decided to create wall mounted bookcases that would be as slim as possible.
I used some 3/4" white pine I had left over from other projects - couldn't be more than a few dollars worth. Each shelf is just 5" deep and spacing between shelves is 7.5". On the sides I cut a dado for each shelf end and then glued it all together (no metal fasteners used). Total construction time including a quick coat of Minwax Polyshades (stain and poly in a single application) was about 90 minutes.
The entire assembly is light and easily attached to a wall with a few angle bracket where convenient.
Paperbacks are light enough that the shelves don't need bracing but if you wanted to add a strip of hardwood for that purpose under each front lip it would be easy to do.
The neat thing about this approach is that the same simple technique will allow you to make any dimensions that will work with whatever wall space you have. So the final look is balanced and uncluttered, leave white space around the shelf you create.
If you don't have a dado blade set/table saw or a router to make the dados, you could do a simple butt joint with a glue block - use wood screws through the glue block to hold everything together until the glue dries.
I have several of these I've made and everyone that sees them compliments me and thinks they must have been expensive, custom-made pieces.
If you've made some custom storage or built-in pieces post a picture and I'll give you an upvote.