>4th best selling lens
>guys is there a better one?
no
the next lenses are the 28-400, 105mm macro, 14-30 f4, 28mm f2.8, 14-24 f2.8, and 180-600.

nobody likes the 35mms at all (nikon has never made a good FX 35mm) with the 40mm as an option
almost nobody likes the 50mm f1.4 ("soul but woah, not too much soul")
nobody likes the 20mm f1.8 or 24mm f1.8 pixel peeper milky way lenses (but fast UWA portraits are a fun meme)

trust the market on this one. the 40mm is very good especially if you know what you're doing. if you have sharpness issues with it return it or consider that when buying used lenses, they have probably been dropped 6ft onto carpet at least once