Spirits aren't particularly seen, rather they're sensed. There's multiple different methods of communicating with spirits, personally I use rituals and meditation. Once you find a reliable method of communication then you can ask it whatever you'd like or talk to it as you see fit. It's important to find a good starting point and work your way from that. There are some spells listed on the site that explain how to communicate and/or summon spirits, of course some of them may not work, though it isn't hurtful to try. Some mixtures of ingredients are given as well but if they contain odd things (such as dirt, I use this as an example because I've seen it before) I'd recommend NOT eating or drinking them, though that's really common sense.
Well, when you state sense, it brings to mind a particular spot in my bedroom. I can feel as if something I'd there watching me, always on this one spot near the bookshelf. I'm not sure if I'm crazy out if its something else.
Sometimes spirits have a strong connection with some of the material objects that they leave behind. If you have any older objects that may have been passed down or bought at a yard sale after a person died that are sitting on the bookshelf, or even the bookshelf itself, then a spirit may be linked to one of those objects. There may be no connection at all to the spirit and an object and the spirit is a deceased family member who's trying to tell you something related to that perticular area of the room or one of the objects on the shelf. There may even be something hidden in one of the books, such as a note, that it wants to be found. Personally, I don't know what you have on the bookshelf, though those are all possible situations.
There's a possibility that one of the older pawned books had some sentimental value to someone before they died. If you're incapable of finding an efficient way of communication then perhaps you should look into each one individually. Maybe move some books around the room in small groups and see if the presence you sense changes along with the position of the books. Also take note that ghosts are physical apparitions while spirits have difficulty appearing visually. There is a difference between them.
Gabauchi, it is possible to see spirits, but it take training for your eyes. At first you may see and sense nothing, but eventually you sense them then learn to see them. Be careful though, as it's hard to tell just starting out what a spirit's intent is. Some say spells work, but I say they amplify faith - which is how it really works. Start meditating to clear your mind and hone your senses.