The reflector length of almost 40cm with LEDs spread evenly over the whole length means it lights up two A4 pieces of paper fully and evenly, so you can clearly read both pages in an open book, and all 88 keys are illuminated. The height from bottom of base to bottom lamp is 42cm, I presume the 'max height' of 39cm listed is the max height you can reach with the neck curved into position... I have it behind the music stand of my digital piano, and it comfortably exceeds the height of the score and extends far enough forward, so that the LEDs can be directed back onto the pages with plenty of room to turn pages. The neck is fully flexible, allowing it to be curved backwards as well, so following the slope of the music stand (that added flexibility means of course that you can also tilt the lamp so far forward that the base can't counterbalance it, but that's not the case for grand/digital piano use).
All that said, unfortunately, the the non-selectable light colour temperature of 2700K is too 'warm' in tone for me... as a beginner and especially when practising, I need the clearest contrast, so I have exchanged this lamp for the Gravity PLT2B which has the 6000K option.