Congratulations on getting your first book out! 
Can you verify that the clicks are in the recording and not in the playback? For example, do you see them on the waveform? Do they appear in exactly the same place every time you replay a phrase?
Usually when this happens, something has changed. 
Curious… how did you do that?
There are others on the forum that can give you better direction than I with your clicks and with audiobook recording, but I know they will want to know which microphone you are using and which USB interface. Do you care to share that information?
For some inspiration while we are waiting for their help, do a forum search (upper right corner) on clicks. Here’s one: Clicks are driving me nuts!