An author of the original book, Allen B. Downey, has released a third edition if his updates that is also available online at no cost and in Allen B. Downey’s words:
The book is now entirely in Jupyter notebooks, so you can read the text, run the code, and work on the exercises – all in one place. Using the links below, you can run the notebooks on Colab, so you don’t have to install anything to get started.
The text is substantially revised and a few chapters have been reordered. There are more exercises now, and I think a lot of them are better.
It’s interesting to see how the same source material has grown into two differently maintained and similar resources.
Some people who are self studying Structure and Interpretation of Computer Programs have been using a discord server to assist each other as needed. I realize that there are a number of people using Lemmy whi are very opposed to using discord over other options, but I don’t know of any other sustained forums focused on this book.
https://discord.gg/j2tCPpMq