The EV adjustment is usually that +/- button. It only applies if you're using an automatic exposure setting.
On my camera, and I'm sure on yours too, there are three automatic exposure settings:
P, or "program mode" is fully automatic. The camera's software will choose a shutter speed (such as 1/125 second), and an aperture (such as f4.0) for you.
Av, or "aperture priority mode" allows you to set the aperture (f-stop, the size of the hole that lets light into your camera), and then the camera automatically chooses a shutter speed for you.
Sv, or "shutter priority mode" allows you to choose the shutter speed, and the camera will set the aperture.
For each of these settings, the EV adjustment will change how the camera chooses the value it chooses. A positive adjustment (+1, for instance) will cause the camera to choose a slower shutter speed (for example, 1/60 second instead of 1/125) or a larger aperture (for instance, f2.8 instead of f4.0 -- smaller numbers mean a larger aperture).. This lets more light in, and results in a brighter picture.
I'm suggesting that you don't use any of these automatic modes, and thus don't use the EV adjustment either, but rather use the M or manual mode, which requires you to set both the shutter speed and the aperture.
You're right that this would leave you with lots of potential combinations to check. I'd suggest that you start by setting your shutter speed to 1/125 second, and shoot with various apertures to find one that works. 1/125 second should be fast enough to get a sharp picture even if the book moves a bit while you're shooting it (the camera shouldn't move, because it's on a fixed mount). If you find a good combination, use it. If all of your pictures are still too dark, try setting the shutter speed to 1/60 and repeat the exercise. I'd be reluctant personally to go with a shutter speed any slower than 1/30 second. At that point, I'd look into adding more lights, but that shouldn't be necessary. I feel confident that if you're using two halogens, you'll be able to shoot at 1/125 second with an f-stop (aperture) that's smaller than the largest one available.
The reason smaller numbers mean larger apertures is because the aperture or f-stop is actually a ratio of the focal length of the lens to the size of the opening. You can think of it as the denominator of a fraction, so just as 1/60 second is "larger" than 1/125 second, f2.8 is "larger" than f4.0. Don't let it confuse you.