With more magnification, fewer words can be be seen at once. The lens tends to be smaller. This can make your arms or neck ache. Holding things close to read can be awkward and tiring, especially if a magnifying glass is needed, but more words come into view. It is often more comfortable holding the magnifying glass further away, even if fewer words are seen.
Good lighting Reading with a good light helps.
The light needs a reflector so the light shines on the book, not into your eyes. A strong light on the ceiling is not particularly helpful. A light with a reflector, angled on to the book is much more helpful. The light needs to be positioned so that glare is reduced and shadows are minimal. If the magnifier is not internally illuminated, a low wattage, eg 40w, lamp close to the table is usually better than a central light from the ceiling.