Neither. I'm a Day-Age old-earth creationist, which is different from traditional gap theories in that gap theories interpret the Hebrew to say "Earth became formless and empty" after creation. A more careful look at the Hebrew makes this unnecessary. A main reason for many gap theories is to unnecessarily explain away evil and death before Adam. There's no theological or scientific justification for a previously judged/ruined Earth, it's simply an attempt to fit the Bible to some particular beliefs in some cases. In other cases, it was just a careless attempt to fit "old-earth" science into the Bible. That can be done without inventing theology like some gap theories do.
Day-age recognizes that the point of view of the writer changes from Gen 1:1 to Gen 1:2. There is an unspecified period of time between these verses, but it doesn't warrant the claims of many traditional "gap" theories.
The author of the book doesn't subscribe to the gap theories or theistic evolution either.
Closing the Gap: A Scientist’s Response to the Gap Theory by theologian John Rea and astronomer Hugh Ross details the history of and problems with gap theories.