He collected the cars and wrote about the (non-fictional) drugs. He wasn't an exhibitionist, as far as I know, so you'll have to infer what you like about the middle one from his writing.

Some related reading:

https://www.theguardian.com/books/1997/may/20/fiction.scienc...

https://www.scotsman.com/news/interview-iain-banks-a-merger-...

https://www.vice.com/en/article/iain-banks-274-v16n12/