In your example, after the market maker posts the BUY 10 @ 100.0, your book is: SELLING 100 shares @ $10.02 SELLING 200 shares @ $10.01 SELLING 10

In your example, after the market maker posts the BUY 10 @ 100.0, your book is: SELLING 100 shares @ $10.02 SELLING 200 shares @ $10.01 SELLING 100 shares @ $10.00 <-- BUYING 100 shares @ $10.00 <-- BUYING 100 shares @ $9.99 BUYING 200 shares @ $9.98 BUYING 100 shares @ $9.97 Wouldn't the SELL and the BUY @ 10.00 get matched immediately in this case?