I'd heard "disruption" thrown around so much that it lost all meaning, so I figured I should go read the actual source. And yeah — Christensen's original framework is way more nuanced and interesting than the Silicon Valley version that gets tossed around at pitch decks.
The core idea: established companies fail not because they're lazy or incompetent, but because they're too good at serving their existing customers. When a disruptive technology shows up, it's initially worse on the metrics that current customers care about. So rational managers rationally ignore it. By the time the new technology improves enough to compete, it's too late. The incumbents' own competence becomes the trap. That's the dilemma — doing the "right" thing (listening to customers, investing in proven markets) leads to failure.
The disk drive industry case study is the most compelling example. Christensen traces multiple generations of disruption — 14-inch to 8-inch to 5.25-inch to 3.5-inch drives — and shows the same pattern repeating each time. The leaders in one generation almost never lead the next. Not because they couldn't build smaller drives, but because their best customers didn't want them. It's a pattern that maps perfectly to tech today — think about how mobile disrupted desktop, or how cloud disrupted on-prem.
My one criticism is that the writing can feel a bit academic and repetitive. Christensen makes his point thoroughly, but he could make it in fewer pages. The case studies start to blur together after a while. Still, the framework itself is genuinely powerful. I catch myself using it constantly now — asking whether something that looks "worse" today might actually be the early stage of a disruptive shift. That mental model alone makes it worth the read.