Is it worth it to publish 1 book at a time?

If you want to go about this professionally, the general advice is not to wait too long between books.

How long did it take you to write this one? If you're a one book a year writer, then I would suggest you wait until you have at least two books, so the sales momentum of the first book (if any) will carry on to your next book. If readers have to wait too long between books, you have a high risk of losing them. This especially goes for fiction.

Again, whether you should publish your finished works at once or stagger them will depend on your writing speed. Staggering them will obviously allow you more time to complete your next work.As a final note, when you say almost done writing, I'm going to assume that your book has been beta-read, revised, and proofread (by someone else than yourself), right? If not, then I would urge you to do this first.

Publish them one at a time.  If people really like the first one, you might be able to raise the price of the second so that people can learn what happens!

There are no rules but one at a time seems reasonable to me.  One good one is way better than three mediocre ones in my opinion.