We tried different models. One book every two months, one or more chapters of a book every month (thus finishing a whole book over a few months), and one article/video (generally requiring an hour of reading/watching time) every two weeks. My thoughts below are based on experience of those three models.

1. Reading a whole book every one or two months works well when everyone has a regular reading habit. Without that people realize that they need to read a whole book in a few days before the meeting. That either led to poor quality discussions or people showing up without reading. 2. Reading book chapters every month was less demanding but the frequency of meetings was still too low for people to build reading into their routines. 3. At two weeks the frequency was high enough that it became a routine for the engineers. 4. We also reminded everyone one day before to read the article. Even if they had forgotten to read till then it is easy to find and hour in the day to read up. 5. If the reminder was too far in advance (say 3 days before) then people ignored the reminder.