The Affordable Care Act includes a long list of codified instructions about what's required under the law. However, like any major piece of legislation, many of the specific details are left up to the agency responsible for implementing the law.
While the PPACA is itself a lengthy document, it would have to be several times longer yet in order to cover every conceivable detail involved in operating the ACA exchanges, Medicaid expansion and so forth. The major provisions of the ACA fall under the Department of Health & Human Services (HHS), and within that, the Centers for Medicare & Medicaid (CMS)
Every year, CMS issues a long, wonky document called the Notice of Benefit & Payment Parameters (NBPP) for the Affordable Care Act. This is basically a list of tweaks to some of the specifics of how the ACA is actually implemented.