DC Studios co-head James Gunn is planting the seeds for a future where Superman, Batman, and Wonder Woman once again share the screen, but fans hoping for that moment right away might want to pump the brakes.

As James Gunn’s highly anticipated “Superman” soars into theaters this month, fans can journey into the DC Universe with a new book about the making of the film. Penned by veteran film author James Field,

“It was just difficult to figure out where I was going to come from with Superman ,” Gunn said speaking to io9 in Los Angeles last week. “And I think that it really started with my dog in a lot of ways. The idea of putting in Krypto, I think, was the fun part for me, because that was something that we hadn’t really seen in a Superman movie.”