Our Standard book / filing shelving contains 6 levels (shelves) per section to the height of 2030mm. The width of a single shelf is 900mm wide and 300mm deep. Each section increases the width(left to right) by 906mm. The shelves are adjustable to accommodate larger items. The gap between shelves are 370mm if spaced evenly as in the picture.
Weight baring is comfortably 100Kg per shelf relating to over HALF A TON (600Kg) per 900mm section. You will not come close to this weight with books or files.