The essential, and the reference guide to the Talmud

I am wondering how the two Talmud works by Rabbi Steinsaltz relate to each other? Is the Reference Guide to the Talmud: Fully Revised supposed to replace The essential Talmud, or are these two different books?

I know that both have older editions, and I thought they were different books. But looking at the previews, I am no longer sure. Would having the first be enough and cover everything that the second one has? TIA.