> I don't think any of these are firm categories and many books have aspects of many sub-genres Agree. Some also vary as they progress. E.g. the Charles Stross

> I don't think any of these are firm categories and many books have aspects of many sub-genres Agree. Some also vary as they progress. E.g. the Charles Stross 'Merchant Princes' sequence that starts out looking like a portal fantasy (people can jump to parallel worlds by looking at a special pattern) but (mild spoiler) becomes quite hard SF as the mechanisms behind the jumping become understood by the protagonists.