bookbuild. can someone explain this?

I'm not entirely clear about what is going on.

"The bookbuild was well supported with a clearing price of $2.00 per New Share, a premium of $0.47 to the Offer Price. Eligible institutional shareholders who elected not to take up their entitlements in the Institutional Entitlement Offer will receive $0.47 for each New Share not taken up (net of expenses and any withholdings required by law)."

Then later...

"Retail shareholders who do not take up their entitlements or who are ineligible to participate in the Retail Entitlement Offer will receive any premium between the clearing price under the retail bookbuild and the Offer Price for New Shares of $1.53 (net of expenses and any withholdings required by law)."

Specifically, my questions are:

1) What does the "clearing price under the retail bookbuild" mean?

2) Are they saying that if I choose not to give them money, they will give me money?

3) If the answer to question 2 is yes, why would I take up any of my entitlement?