How serious is hepatitis a?

Can be. Hepatitis a can lead to hospitalization and, rarely, to death. However, most often it gets better 'by itself' with so-called supportive measures. Remember it is infectious. Famuiily/contacts shoudl be immunized. Certain jobs should nto be held while infectious (cook for example...). Get better. Avoid etoh. Drink plenty. Eat blandly (your taste will probably be 'off''). Avoid with vaccine...
No chronic forms. Hepatitis a is a liver infection that will make you miserable for awhile with nausea, vomiting, stomach ache, diarrhea , jaundice. There is no consequences or chronic forms however. So it's not much worse than your trivial stomach bug with vomiting/ diarrhea for a couple of days.