Is it a good idea to work on two books at once, or is it better to do it one at a time?

It’s a good idea to do whatever gets your ass in a chair writing.

Stop looking for the secret to writing a book. There isn’t one. Do what works for you.

Some writers focus best when they work on one book at a time. Some writers find they are more productive when they switch between books. If you want to be a writer, find what works best for you, and do that.