If you publish two books, then you will have published one bad book. Actually, if you publish two books, you will have published two bad books. Some of your readers are going to say, "I loved his first book way more than his second." Other readers are going to say, "I loved his second book much better."
The only way to get out of this conundrum is o publish one book, and make sure everyone loves it. I can think of Harper Lee's To Kill a Mockingbird. That's it. Who doesn't love that book? Answer: racists and crazy people.