[grueful]

Books are typically quite a bit out of date if it's a rapidly progressing field.

More stuff ends up in journal articles, but about a year or so behind the actual work, and at a level of detail which is often problematic to reproduce. You typically have to treat it as a reverse engineering problem - but once you know the core ideas, that's often possible.

Then there's the mountain of "trade secrets" which never get published anywhere. A lot of compelling work in e.g. graphics falls under this case - although you might see a demo and overview at SIGGRAPH.

Publishing tends to be a net positive for serious commercial research work, even if the release has to be delayed. It's a solid process for documenting internal knowledge. It's also one of the main things that's going to interest other researchers in working for you.