You should filter out authors from the input books in the output. If liked a book by an author, surely I'd read more of their work if I wanted to — recommending them isn't helpful. Along the same lines, I think interesting recommendations tend to be the ones that (1) I like and (2) I didn't expect. The more similar the recommendations are to the input, the more likely I already know them, and the more likely to creat…
VERY few authors write consistenly good books.
If you liked one book by an author, it is not at all likely that you will like the other books as well. For example, Neil Stephenson is probably my favorite author alive today, but I hate almost half of his books.
The only author that I can think of where I read and liked every single book was Terry Pratchett, and that might have be a case of "I was still young and easy to impress".