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. The normal public issue is also referred to as the fixed price issue where the issue price is known and determined in advance and is also communicated to the potential IPO investors. In case of Book Building, the demand can be known everyday as the book is built. But in case of the public issue the demand is known at the close of the issue. The final price is discovered only after the book is completely built and the price is discovered based on the level that elicits full and maximum demand. The issue will only communicate the bidding range and IPO investors are allowed to bid in that range. Any bid outside the range is automatically rejected. However, if you bid lower than the discovered price then the allotment will not be made. The best way is to bid at the cut-off price which is like acceptance that you are willing to accept the discovered price.