Warped pages are normal and the result of heightened tension. To help alleviate this, try loosening the pages so the tension is more evenly distributed. You can do this by opening the lamp fully and gently pulling the pages from the center outward. You might also open the lamp all the way, gather the last few pages of each side, paper clip them to the cover, and allow them to sit overnight. This tension tends to lessen with time and use.