Accept an invite to write a book chapter?

[mleok]

Don't waste time on a book chapter outside your main area of research (or even within it, to be honest). Focus on journal publications and grants.

[artalot]

Another "depends on your field and tenure requirements post." Several of my publications have been book chapters, but this is common in my subfield. Also, people keep asking me and during COVID it's been nice to have someone come to me with an idea and a firm deadline since I was so burned out. All but one of my essays have been editorially and peer reviewed, meaning that I actually get more feedback, which was helpful early in my career.
One of the pluses is that don't have to shop it around to journals, you pretty much know it will get into the essay collection. This is also why people are saying they don't count as much - the volume tends to be accepted on the strength of the collection rather than on individual essays. That said, I disagree with those who say they shouldn't count. Scholarship should be about quality, not publication venue. I've read some truly awful journal articles, so I don't think journals are a guarantor of quality.
As other have said, some of them do take a lot of time to come out and that is dependent upon the editor(s) and other contributors. I had one come out in less than a year, which is faster than a journal in my field; another took 4 years. IF you do it, make sure to check whether and how 'in process' work can count. For my process it counted as evidence of sustained scholarship, which was required, but not as evidence of research excellence.

[Ruralguy]

Even in the physical sciences there are a number of prominent (and less prominent) practitioners who wrote well read chapters or entire books. Probably most had tenure or the equivalent at some lab, but not all had won full prof or prominent chair yet, so it could be that they worked at least a little bit against the grain to do something useful for the field. Not that I'd suggest it pre-tenure for more or less anybody at an R1, or even much of anywhere, but beyond that, its a valid choice.