From my list;
2 Fiction
2.1 Action
2.2 Westerns
2.3 Children
2.4 Fantasy
2.5 Historical Fiction
2.6 Horror
2.7 Humor
2.8 Mystery and Crime
2.9 Other fiction
2.10 Romance
2.11 Science Fiction
2.12 Short Fiction
2.13 Young Adult
Keep meaning to do a more definitive list, but the problem with defining lists is its an infinite black hole of time suckage :/
For instance, does erotic fiction come under romance or does it need its own category and without that do you want straight/gay/BDSM etc etc. Urban fantasy is currently a 'thing' so again, do we have a new category or use fantasy-mystery & crime-horror tags?
Another tag I've seen used occasionally is 'womens fiction' - I allways thought it as devisive as a 'men's fiction' tag but thats just my opinion so may be valid for a lot of people.
Bottom line, I try to keep a simple fiction list as I tend to prevaricate if I think about it too much
Edit: forgot to add military fiction as a tag - I don't use it for myself as I don't like the genre but I guess it should be on the list.