"It is a good book."
Translation:Det är en bra bok.
Yes, you could say god bok in some contexts, but it’s most common to say bra. If you use god you stress much more that it’s a personal favourite that you really enjoy reading. Whereas bra bok is more objectively ’good book’.
When people talk about god bok it’s often the whole experience of reading it, and you often hear it in contexts such as ’a cup of coffee and a good book’, ’lie in the sun reading a good book’, ’to enjoy a good book’ etc., whereas if you’d just walk up to someone and say ’that’s a good book’, you would use bra.
This is my experience as a native speaker by the way, the connotations might vary for another speaker.
I agree, it still ’survives’ in the sense ’of good quality’ with plenty of words, but it can almost always be replaced by ’bra’ when you talk about the quality of something, which I also write in the post above: ’god/bra kvalitet’, ’god/bra simmare’, ’god/bra idé’, ’gott/bra minne’. Bra is probably more common in all of these phrases.