You're right, that also made me wonder. It isn't really plausible that Vito lay in hospital for more than a year. First of all, it wasn't safe for Vito to be there as his rivals tried to murder him. Secondly, I don't think a recovery would take so long, altough I'm not a doctor. But for me, certain time references like "1947" and "1948" are undisputed facts and difficult to ignore. It is as Puzo wrote different storylines altogether, each with different timelines. That makes it so confusing. Like TB said, there are so many to choose from, so it's just which one you prefer to believe.