Just my personal opinion, having only read the synopsis of the book, watching the show and a couple YouTube videos with theories..
It's a story of people having to directly face the ramifications of their actions.. the ramifications are clearly ongoing, so they could very easily have a 2nd season leading directly from this, court cases and everything that surrounds that.. Hannah and the tapes were just the 'big bang' in a sense
The format obviously changes a bit, without going through the tapes to that extent and Hannah herself being that involved.. but we got a glimpse of that throughout the series and specifically in the finale when clay goes to see Kevin
Obviously we'll have whatever steps Hannah's parents now take.. clay's mother will eventually hear as well, which will lead to decisions on her part.. then guidance counselor could go any number of ways
Tyler is obviously their big play.. but there is a ton there if they don't go that route material wise for at least 1-3 more seasons