What is the main difference between offer of shares through book building and offer of shares through normal public issue?

Price at which securities will be allotted is not known in case of offer of
shares through Book Building while in case of offer of shares through normal
public issue, price is known in advance to investor. Under Book Building,
investors bid for shares at the floor price or above and after the closure of
the book building process the price is determined for allotment of shares.
In case of Book Building, the demand can be known everyday as the book
is being built. But in case of the public issue the demand is known at the
close of the issue.