Unrelated to Wren, but I felt that Bob's book "Game Programming Patterns" ([1] and a free web version [2]) was excellent, and a very down to earth treatment of the topic. All of the examples were relevant and pretty hard hitting.

I know patterns (especially "design patterns") have become a bit of a swear-word, something which hints at severe engineering malpractices, especially along the lines of introducing unnecessary complexity for seemingly its own sake. I think that view oversimplifies the topic greatly, so hopefully people don't dismiss it at face value.

[1] http://gameprogrammingpatterns.com/ [2] http://gameprogrammingpatterns.com/contents.html