As you might assume, good bookshelf speakers are smaller versions of the large tower speakers. They are referred to as bookshelf models obviously due to their size and weight and the simple fact that in most cases they can actually fit on a bookshelf.
This made them especially popular for apartment dwellers and due to their size, they actually fit nicely into a surround sound or home theater speaker system.
In most cases, they will offer excellent sound quality. They normally are in the 2-way or 3-way configuration and will give good performance in a relatively small package. Also, a good point is they will be substantially less expensive than tower speakers in most circumstances.
An additional benefit is the better brand 3-way bookshelf speakers can easily be placed on 14″ stands and will perform nicely in home theater surround sound setups. They will fill in nicely for the front left and right and if space is available, can easily be used for rear channel speakers as well. The listener will surely be impressed with the overall sound quality when teamed with a subwoofer in this configuration.