The typesetting is terrible in the kindle edition:
1) Equations appear as a (low quality) scan- they are rather gray and the resolution is bad. This is a problem for sub/superscripts in particular.
2) The math symbols in the text vary widely in quality; some are correctly identified and treated as text, but others as scanned images- even within the same equation. This is a problem because the scanned parts are not lined up with the text-like symbols, making things appear as sub/superscripts when they are not. Also, consistently, right brackets (<) are three times the height of other things, including | and left brackets (>), which makes Dirac's notation difficult to read in a glance.