Front facing book displays are a popular option for kids' books. It makes it easier for them to identify the books they want to read. So what if you only have a standard bookcase?
Maybe you have one of the ubiquitous IKEA Billy bookcases somewhere in the house that can be repurposed. If so, just affix a few strips of moulding from your local hardware store to each shelf. For less than $20 (depending on the size of the bookshelf), you get an instant book display.