I like to do my own reading.
To sum it up, inbreeding magnifies the genes in a gene pool. Think of it like a roomful of apples…. If there is a single rotten apple, eventually all the apples will become rotten. The more rotten apples, the quicker all the apples will rot. However, in the end, all the apples will eventually rot. Similarly, depending on the type of genes in the original gene pool, the amount of time for fatal outcomes to appear will vary, but sooner or later, it will create a depression due to those harmful genes.