There are many pros to collaboration when it comes to writing, but it is not something everyone can do. Peter David, who is best known for being a comic book writer, said that he found writing prose novels much more fulfilling, as that’s a product that he completes all on his own, as opposed to a comic which is a collaboration with an artist.
Jeph Loeb is another comic book writer (though he’s written other thing as well, and currently heads Marvel’s television decision), and being a comic book writer, his work requires much collaboration. He used to be known as an amazing writer, until his son passed away. His work was never the same again. Some people say it broke him, and he never recovered. I don’t know if that’s true. But something I found interesting about his work, specifically in comics. It became very obvious after a while that he was writing for the artist, often at a disservice to the story. There was no reason for a time traveling Kingdom Come Superman to show up in Superman/Batman: Public Enemies, but the artist wanted to draw him, so he was written in. Batman: Hush, another one of his works, is overly crowded with villains, but most puzzling of all was an appearance by Jason Todd, a former Robin who was dead at the time of it’s publication (don’t worry, he got better. Comic books and all that). It was later revealed that it was Clayface impersonating Jason, but the only reason he was there was because the writer wanted to draw him. And in Loeb’s Supergirl book, he has Supergirl fight the Barbara Gordon version of Batgirl, who was paralyzed at the time and thus no longer Batgirl (don’t worry, she also got better). The only reason that was written was so the artist could draw a character he wanted, even if it didn’t make sense in the concept of the story. (Again, it was revealed to be Clayface in disguise. Boy, Loeb sure relies on that Clayface gimmick a lot.) A successful collaborator should put the story before pleasing his or her partner.
Having two names on a book is good, if only for marketing purposes, as it would lead fans of one individual author to check out the other author’s solo work. But honestly, I don’t know how two people can write a book together, other than switching off chapters or something. Plotting though, can be done together with another. I enjoy talking through the story with my wife. Its fun, and we get to bounce ideas off each other. In fact, my favorite part of A Spark Ignites was actually her idea (or taking my idea and pushing it one step farther). Using a collaborator can also help you catch plot holes. There are some people who have to do everything by themselves. I used to be one of them. But even if you want to do all the writing yourself, I’ve found that when it comes to working through a story, two heads are better than one.