Correção de "conditional sentence"

Hi, there! In an FCE pratice test, I've found a sentence that really got me confused as I think the verb "booking" should be used instead of "book", as it would be the subject of the result clause in the conditional sentence. See if you agree with me, or explain to me why it is correct:

"If you don't want to do that, book a timed-entry ticked for 10.30 a.m. Gallery 2, on the fourth floor, is your goal".

Thanks a lot!