Sit back and enjoy it for a minute. Next begins the second stage of the process, because process is what it is. My friend, Pam, speaks of writing being a craft. She is so right. If a carpenter makes a table, much of the work only begins when the rudimentary version is finished.
Your book will need editing - first editing. Read through it fairly quickly, as though you were another reader. This gives you an overall feel for the flow and also any big plot flaws. If you find something, don't panic. It won't be as difficult to correct as you fear. You will also see any repetitions. This is a sobering experience but it is an essential step along the way. Try not to do any correcting or active editing at this point but it's OK to make some notes. If you're anything like me, you will have some omissions, names you've forgotten, things you didn't want to break the flow to look up when you were writing. Finding them again can be a little disconcerting but don't worry. Your next, big edit will sort them out.