Really, almost any miniseries or ongoing series would be a better choice. I think the only one worse than Double Helix is New Earth? Maybe Day of Honor.
At least the individual Double Helix books had an ending. Gateways left things hanging to be resolved in a separate novel. The New Frontier one is the only one I read, and I have no idea how it was resolved (I suppose it says a bit that I have never bothered to look it up, but I was annoyed at the time).
To give a New Frontier example, when Peter wrote House of Cards, he had no idea what actually happened on the Grissom when Calhoun served there. It was, in essence, a placeholder which would be a springboard for Future Peter to tell a story when the opportunity presented itself. Said opportunity came in the Captain's Table miniseries.
I recall getting that impression from a line in one of the prior books, "Beg me like the captain of the Grissom begged you"; I don't think the captain ever begged Calhoun at all.