book (on) out

To leave a location very quickly. He booked on out the back door as soon as he saw his ex-girlfriend walk into the party. I booked out of the house when I realized that I was going to be late for my appointment. The train leaves in five minutes? Oh man, I better book on out of here then!

book in

To register oneself for something, as at a hotel or some activity. Same meaning as "check in." Our plane arrives at 9 AM, but we can't book in to our hotel until noon. Remember, we have to book in at the festival or we won't be allowed in. Tara is booking in for the exam at the registration table.

book it

slang To flee or depart very rapidly. The cops will be here any minute. Let's book it! I booked it after breakfast so that I wouldn't miss my bus. The lecture starts in five minutes, so you're going to have to book it to make it on time!

book up

To reserve all available spots or options. A noun or pronoun can be used between "book" and "up." Well, that hotel is all booked up, so we'll have to look for a room somewhere else. If all of today's slots are booked up, you'll have to come back and meet with me tomorrow. Do you really expect me to believe that every single one of your rental cars is booked up for this weekend?

book something up

to reserve all the available places. The travel agency booked all the good seats up. Who booked up all these seats?

book up

To reserve all the available places or times, such as seats, rooms, or appointment hours, from something or someone: We couldn't get a place to sit because someone had booked up the entire restaurant. There are only two small hotels on the island, and their regular customers book them up a year in advance. You'll never get an appointment; the doctor is booked up through the next month.