For a myopic person the least distance of distinct vision maybe the same 25 cm. So if you use the lens formula and calculate where the book must be kept to form an image at 25 cm, the distance is about 36 cm. So that’s the first problem reading a book with specs on for the person.
Secondly, the angle subtended by the image(at 36cm) on the man’s eye is on an average less than that it would subtend at 25 cm. This can be shown with the help of this image
In the image, the ball that is further away subtends a smaller angle. @Prakhar_Gupta