Eric, welcome aboard.
Knowing your capabilities and preferences makes a difference here. If you can spray, then some products make sense, but if you can't, then other products make sense.
I think most of the products recommended so far are wiping or brushing products - at least as far as I know. I personally prefer to avoid solvent based products, so that narrows my choice considerably.
I have finished table tops with Target's Coatings (sprayed) conversion varnish and lacquer. Both worked well, but neither has been used extensively As A Writing Desk. Both have held up to everyday usage. But that advice does not help if you can't spray.
There are lokely several good choices for you.