It is probably the light
Most lamps use a blue LED chip that cannot reproduce the full visible spectrum. The wavelengths your eyes rely on most for reading are simply not there, so your brain fills in what is missing. That effort is why reading feels harder by evening.
The HD Original uses a purple chip that reconstructs every wavelength of natural daylight. On the standard measure of colour rendering, where sunlight scores 100, the HD Original scores 98. A typical household LED rarely gets above 80. The result is light that feels natural rather than artificial. Small print sharpens, colours look right, and for many readers the fatigue that used to build through the evening stops coming.