To obtain an almost scanner-like image with minimal set up I'd locate two lamps either side of the paper. And then while taking the photo, locate the lens of the phone/tablet directly towards the center of the sheet. That is, if you place the sheet of paper flat on a table, the lens must be directly above the center of the page.
The wide angle lens in most phones exaggerates perspective distortion, that is, your rectangular piece of paper wont show as a rectangle in the photo, but as a trapezoid. The side of the sheet that is further away from the lens will be smaller on the photo. You correct this by placing the lens equidistant from all four corners when taking the image.
I make emphasis in locating the lens because many people do not realize the lens is (usually) on a corner of the phone or tablet, and try to center the phone respect to the paper. Just that small inch and half distance from center of phone to the lens is enough to distort the image due to perspective.
The idea of locating two lamps is to achieve the most uniform lighting possible. Ideally, both lamps should be the same size and power. That makes things easier because if lamps are equal, you only need to place them both at the same distance from the sheet of paper.
I'm thinking of just two simple desk lamps. Place them such that the bulb is 12-8 inches (13 - 20 cm) from the border of the sheet horizontally and vertically, and about the middle of the height of the page.
It will also help if you leave a margin while writing, so no information is lost if the picture does not cover 100% of the page, that allows you to close up a little bit more and "cropping" part of the page (think leaving up to 1/4 of an inch or 0.5 cm out of the picture). This lessens the risk of showing the dark thing that supports your page/notebook.
Of course, you can also put a white "background" under the notebook, so if the capture includes more than just the page, it wont be a problem.
Try as best as you can of flattening the pages before taking the picture. I realize this can be tricky or impossible with some notebooks. The white patch in your example picture is because at that point, the curvature of the page makes the angle of incidence/reflection of light match the direction of your lens. (Read on angle of incidence and angle of reflection) That is why I recommend placing the lamps at the sides at roughly 45 degrees from the center of page, so the reflection goes to the other side, away from the lens. But if flattening the pages results in much of a hassle, try placing the lamps above and bellow the page, to lessen the chance of direct reflection due to the bend o pages.
Note: The two lamps idea is to allow to take the pictures at any time, but if you do it during the day, a nice unobstructed window is a very nice source of light, specially on an overcast day.